Today the iMac is even worse, to open any internet items it runs at a 'snail pace' because the blue bar along the top almost seems to stop then suddenly completes:-

Here's today's report:-
EtreCheck version: 3.4.5 (455)
Report generated 2017-09-25 10:01:47
Download EtreCheck from https://etrecheck.com
Runtime: 10:57
Performance: Poor
Click the [Lookup] links for more information from Apple Support Communities.
Click the [Details] links for more information about that line.
Click the [Remove/Report] links to remove adware or update the whitelist of legitimate software.
Click the [Clean up] link to delete unused files.
Problem: Computer is too slow
Hardware Information:ⓘ
iMac (27-inch, Late 2012)
[Technical Specifications] - [User Guide] - [Warranty & Service]
iMac - model: iMac13,2
1 2.9 GHz Intel Core i5 (i5-3470S) CPU: 4-core
16 GB RAM Upgradeable - [Instructions]
BANK 0/DIMM0
8 GB DDR3 1600 MHz ok
BANK 1/DIMM0
8 GB DDR3 1600 MHz ok
BANK 0/DIMM1
Empty
BANK 1/DIMM1
Empty
Handoff/Airdrop2: supported
Wireless: en1: Unknown
Video Information:ⓘ
NVIDIA GeForce GTX 660M - VRAM: 512 MB
iMac 2560 x 1440
Disk Information:ⓘ
APPLE HDD WDC WD10EALX-408EA0 disk0: (1 TB) (Rotational)
[Show SMART report]
EFI (disk0s1 - MS-DOS FAT32) <not mounted> [EFI]: 210 MB
MacintoshHD (disk0s2 - Journaled HFS+) / [Startup]: 983.21 GB (632.99 GB free)
Recovery HD (disk0s3 - Journaled HFS+) <not mounted> [Recovery]: 650 MB
eDrive (disk0s4 - Journaled HFS+) /Volumes/eDrive : 16.00 GB (2.85 GB free)
USB Information:ⓘ
USB20Bus
hub_device
Apple, Inc. Keyboard Hub
Mitsumi Electric Apple Optical USB Mouse
Apple Inc. Apple Keyboard
VIA Labs, Inc. USB2.0 Hub
Tablet PTZ-431W
Apple Inc. FaceTime HD Camera (Built-in)
USB20Bus
hub_device
hub_device
Apple Inc. BRCM20702 Hub
Apple Inc. Bluetooth USB Host Controller
USB30Bus
VIA Labs, Inc. USB3.0 Hub
Western Digital My Book 1140
My Book 1140 disk1: (1 TB)
EFI (disk1s1 - MS-DOS FAT32) <not mounted> [EFI]: 210 MB
1TB MyBook Bacups for Time Machine (disk1s2 - Journaled HFS+) /Volumes/1TB MyBook Bacups for Time Machine 1 : 999.83 GB (16.54 GB free)
GenesysLogic USB3.0 Hub
GenesysLogic USB3.0 Hub
Apple Inc. MacBook Air SuperDrive
GenesysLogic USB2.0 Hub
GenesysLogic USB2.0 Hub
USB2.0 Hub
Thunderbolt Information:ⓘ
Apple Inc. thunderbolt_bus
Apple Inc. Thunderbolt to FireWire Adapter
System Software:ⓘ
macOS Sierra 10.12.6 (16G29) - Time since boot: less than an hour
Configuration files:ⓘ
/etc/sysctl.conf - File exists but not expected
Gatekeeper:ⓘ
Mac App Store and identified developers
Possible adware:ⓘ
Adware: ~/Library/LaunchAgents/pronto.notification.plist
Adware: ~/Library/LaunchAgents/pronto.update.plist
2 possible adware files found. [Remove/Report]
Clean up:ⓘ
/Library/LaunchDaemons/com.nvidia.cuda.launcher.plist
/Library/PreferencePanes/CUDA Preferences.prefPane/Contents/Resources/CUDAd.sh start
Executable not found!
One orphan file found. [Clean up]
Kernel Extensions:ⓘ
/Library/Extensions
[loaded] com.malwarebytes.mbam.rtprotection (3.0 - SDK 10.12) [Lookup]
/System/Library/Extensions
[not loaded] com.nvidia.CUDA (1.1.0) [Lookup]
[not loaded] com.wacom.kext.wacomtablet (Wacom Tablet 6.3.8-2 - SDK 10.9) [Lookup]
[not loaded] org.dungeon.driver.SATSMARTDriver (0.8 - SDK 10.6) [Lookup]
System Launch Agents:ⓘ
[not loaded] 6 Apple tasks
[loaded] 185 Apple tasks
[running] 94 Apple tasks
System Launch Daemons:ⓘ
[not loaded] 41 Apple tasks
[loaded] 176 Apple tasks
[running] 101 Apple tasks
Launch Agents:ⓘ
[running] com.malwarebytes.mbam.frontend.agent.plist (Malwarebytes Corporation - installed 2017-09-22) [Lookup]
[failed] com.nvidia.CUDASoftwareUpdate.plist (NVIDIA Corporation - installed 2017-01-24) [Lookup]
Launch Daemons:ⓘ
[running] com.bjango.istatmenusdaemon.plist (Marc Edwards - installed 2015-05-11) [Lookup]
[loaded] com.bombich.ccc.plist (Bombich Software, Inc. - installed 2014-12-28) [Lookup]
[running] com.bombich.ccchelper.plist (Bombich Software, Inc. - installed 2017-09-19) [Lookup]
[running] com.malwarebytes.mbam.rtprotection.daemon.plist (Malwarebytes Corporation - installed 2017-09-22) [Lookup]
[running] com.malwarebytes.mbam.settings.daemon.plist (Malwarebytes Corporation - installed 2017-09-22) [Lookup]
[running] com.micromat.CheckmateIdleDaemon.plist (Micromat, Inc. - installed 2017-07-04) [Lookup]
[running] com.micromat.CheckmateWorkerDaemon.plist (? ? ? - installed 2017-07-04) [Lookup]
[loaded] com.micromat.MacCheckWorkerDaemon.plist (? ? ? - installed 2017-07-06) [Lookup]
[loaded] com.microsoft.autoupdate.helper.plist (Microsoft Corporation - installed 2017-07-16) [Lookup]
[failed] com.nvidia.cuda.launcher.plist (? 20f73770 0 - installed 2017-01-24) [Lookup] - /Library/PreferencePanes/CUDA Preferences.prefPane/Contents/Resources/CUDAd.sh: Executable not found!
[loaded] com.nvidia.cudad.plist (NVIDIA Corporation - installed 2017-01-24) [Lookup]
[running] com.speedtools.scheduleagent.plist (? f676e844 86494c11 - installed 2017-06-25) [Lookup]
User Launch Agents:ⓘ
[loaded] Yofitofix.AppVemoral.plist (Shmulik Corsair - installed 2017-09-24) [Lookup]
[loaded] Yofitofix.btvlit.plist (Shmulik Corsair - installed 2017-09-24) [Lookup]
[loaded] Yofitofix.disable.plist (Shmulik Corsair - installed 2017-09-24) [Lookup]
[loaded] Yofitofix.dolnwoad.plist (Shmulik Corsair - installed 2017-09-24) [Lookup]
[loaded] Yofitofix.uadpte.plist (Shmulik Corsair - installed 2017-09-24) [Lookup]
[loaded] com.adobe.ARM.[...].plist (? 560d19c8 ac8ed034 - installed 2017-09-21) [Lookup]
[running] pronto.notification.plist (Adam Barrettislav - installed 2017-09-24) Adware! [Remove/Report]
~/Library/Application Support/ProntoApp/ProntoApp.app/Contents/MacOS/ProntoApp
[loaded] pronto.update.plist (Adam Barrettislav - installed 2017-09-24) Adware! [Remove/Report]
~/Library/Application Support/ProntoApp/ProntoApp.app/Contents/MacOS/ProntoApp
User Login Items:ⓘ
CCC User Agent Application (Bombich Software, Inc. - installed 2017-09-19)
(~/Desktop/Carbon Copy Cloner.app/Contents/Library/LoginItems/CCC User Agent.app)
Internet Plug-ins:ⓘ
AdobePDFViewerNPAPI: 11.0.21 (installed 2017-08-09) [Lookup]
OfficeLiveBrowserPlugin: 12.3.6 (installed 2013-03-14) [Lookup]
QuickTime Plugin: 7.7.3 (installed 2017-07-21)
AdobePDFViewer: 11.0.21 (installed 2017-08-09) [Lookup]
WacomTabletPlugin: WacomTabletPlugin 2.1.0.6 (installed 2014-04-16) [Lookup]
EPPEX Plugin: 10.0 (installed 2016-04-04) [Lookup]
Safari Extensions:ⓘ
[not loaded] AdBlock - BetaFish, Inc. - https://getadblock.com (installed 2015-09-26)
[not loaded] Adblock Plus - Eyeo GmbH - https://adblockplus.org/ (installed 2015-09-25)
[not loaded] Nectar Toolbar - AIMIA Coalition Loyalty UK Ltd - http://www.aimia.com (installed 2014-08-09)
[enabled] WOT - WOT Services Ltd - http://www.mywot.com/ (installed 2016-01-04)
3rd Party Preference Panes:ⓘ
Flip4Mac WMV (installed 2008-08-15) [Lookup]
Perian (installed 2009-07-26) [Lookup]
WacomTablet (installed 2015-10-03) [Lookup]
Time Machine:ⓘ
Skip System Files: NO
Mobile backups: OFF
Auto backup: YES
Volumes being backed up:
MacintoshHD: Disk size: 983.21 GB Disk used: 350.22 GB
Destinations:
1TB MyBook Bacups for Time Machine [Local]
Total size: 999.83 GB
Total number of backups: 40
Oldest backup: 05/06/2017, 12:51
Last backup: 25/09/2017, 09:27
Size of backup disk: Too small
Backup size 999.83 GB < (Disk used 350.22 GB X 3)
Top Processes by CPU:ⓘ
8% CheckmateWorkerDaemon
4% kernel_task
3% mds_stores
3% WindowServer
0% ps
Top Processes by Memory:ⓘ
991 MB kernel_task
411 MB mds_stores
285 MB CheckmateWorkerDaemon
131 MB Adobe Bridge CS4
115 MB Finder
Top Processes by Network Use:ⓘ
Input Output Process name
56 KB 9 KB mDNSResponder
9 KB 7 KB apsd
2 KB 4 KB usbmuxd
2 KB 1 KB netbiosd
960 B 1 KB ntpd
Top Processes by Energy Use:ⓘ
7.24 CheckmateWorkerDaemon
4.58 WindowServer
2.06 mds_stores
0.96 CheckmateIdleDaemon
Virtual Memory Information:ⓘ
12.02 GB Available RAM
16 MB Free RAM
3.98 GB Used RAM
12.00 GB Cached files
15 MB Swap Used
Software installs:ⓘ
SATSMARTDriver: (installed 2017-08-27)
Adobe Reader XI (11.0.22): (installed 2017-08-28)
CUDA 8.0: (installed 2017-09-19)
DaVinci Resolve Panels Installer v1.1.1: (installed 2017-09-19)
DaVinci Resolve: (installed 2017-09-19)
Bitdefender Virus Scanner: 3.9 (installed 2017-09-21)
Malwarebytes for Mac: (installed 2017-09-22)
Install information may not be complete.
Diagnostics Information:ⓘ
2017-09-24 16:41:58 Microsoft Excel.app Crash [Open]
Cause: dyld: launch, loading dependent libraries
2017-09-24 14:55:24 iDVD 2.app High CPU use [Open] [Details]
2017-09-24 10:34:23 quicklookd.app Crash [Open]
Cause: quicklookd seems struck trying to quit, crashing
abort() called
2017-09-23 17:02:04 com.apple.WebKit.WebContent Crash [Open]
Cause: Bundle controller class:
BrowserBundleController