suddenly slow wifi connection

For the last few days I've had dramatically slower network connection using my iMac. Network connections on my iPhone and iPad work just as fast as normal, as do other people's connections here at my home. In addition, when I boot my system it takes quite some time for the WiFi connection to get established.

I can't think what I've changed (but there must be something, right?). So I downloaded Etrecheck (which itself took almost 10 minutes). The output is below. I'd be grateful for suggestions on how to solve this.

EtreCheck version: 2.9.12 (265)

Report generated 2016-06-11 12:48:30

Download EtreCheck from https://etrecheck.com

Runtime 1:46

Performance: Excellent

Click the [Support] links for help with non-Apple products.

Click the [Details] links for more information about that line.

Problem: No problem - just checking

Hardware Information:ⓘ

iMac (27-inch, Late 2012)

[Technical Specifications] - [User Guide] - [Warranty & Service]

iMac - model: iMac13,2

1 3.2 GHz Intel Core i5 CPU: 4-core

32 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

8 GB DDR3 1600 MHz ok

BANK 1/DIMM1

8 GB DDR3 1600 MHz ok

Bluetooth: Good - Handoff/Airdrop2 supported

Wireless: en1: 802.11 a/b/g/n

Video Information:ⓘ

NVIDIA GeForce GTX 680MX - VRAM: 2048 MB

iMac 2560 x 1440

System Software:ⓘ

OS X El Capitan 10.11.5 (15F34) - Time since boot: less than an hour

Disk Information:ⓘ

LaCie 2big v2 THB USB3 Raid 1 disk2 : (6 TB) (Rotational)

EFI (disk2s1) <not mounted> : 210 MB

Lacie1 (disk2s2) /Volumes/Lacie1 : 6.00 TB (1.03 TB free)

APPLE HDD ST3000DM001 disk1 : (3 TB) (Rotational)

EFI (disk1s1) <not mounted> : 210 MB

Recovery HD (disk1s3) <not mounted> [Recovery]: 650 MB

Macintosh HD (disk3) / : 3.11 TB (2.63 TB free)

Core Storage: disk0s2 120.99 GB Online

Core Storage: disk1s2 3.00 TB Online

APPLE SSD SM128E disk0 : (121.33 GB) (Solid State - TRIM: Yes)

EFI (disk0s1) <not mounted> : 210 MB

Boot OS X (disk0s3) <not mounted> : 134 MB

Macintosh HD (disk3) / : 3.11 TB (2.63 TB free)

Core Storage: disk0s2 120.99 GB Online

Core Storage: disk1s2 3.00 TB Online

MARVELL VIRTUALL ()

USB Information:ⓘ

Apple Inc. BRCM20702 Hub

Apple Inc. Bluetooth USB Host Controller

Apple Inc. FaceTime HD Camera (Built-in)

Lexar USB_3_0 Reader

Thunderbolt Information:ⓘ

Apple Inc. thunderbolt_bus

LaCie 2big TBT2 USB3

Gatekeeper:ⓘ

Mac App Store and identified developers

Kernel Extensions:ⓘ

/System/Library/Extensions

[not loaded] com.GenesysLogic.driver.GLLUD (8.8.8 - SDK 10.6 - 2016-06-03) [Support]

[loaded] com.LaCie.ScsiType00 (1.5.1 - SDK 10.5 - 2016-06-03) [Support]

[loaded] com.logmein.driver.LogMeInSoundDriver (4.1.4899 - 2016-06-03) [Support]

System Launch Agents:ⓘ

[not loaded] 7 Apple tasks

[loaded] 154 Apple tasks

[running] 77 Apple tasks

System Launch Daemons:ⓘ

[not loaded] 43 Apple tasks

[loaded] 154 Apple tasks

[running] 93 Apple tasks

Launch Agents:ⓘ

[not loaded] com.adobe.AAM.Updater-1.0.plist (2016-03-24) [Support]

[failed] com.adobe.ARMDCHelper.cc24aef4a1b90ed56a...plist (2016-05-14) [Support]

[failed] com.canon.MFManager.plist (2012-05-22) [Support]

[running] com.epson.Epson_Low_Ink_Reminder.launcher.plist (2012-05-13) [Support]

[running] com.epson.eventmanager.agent.plist (2012-05-08) [Support]

[loaded] com.google.keystone.agent.plist (2016-03-03) [Support]

[running] com.lacie.LaCieDesktopManagerAgent.plist (2016-06-11) [Support]

[running] com.logmein.logmeingui.plist (2015-03-27) [Support]

[loaded] com.logmein.logmeinguiagent.plist (2015-03-27) [Support]

[not loaded] com.logmein.logmeinguiagentatlogin.plist (2015-03-27) [Support]

[loaded] com.oracle.java.Java-Updater.plist (2014-04-12) [Support]

[loaded] com.paragon.updater.plist (2015-03-18) [Support]

[not loaded] com.teamviewer.teamviewer.plist (2015-03-20) [Support]

[not loaded] com.teamviewer.teamviewer_desktop.plist (2015-03-20) [Support]

Launch Daemons:ⓘ

[loaded] com.adobe.ARMDC.Communicator.plist (2016-05-14) [Support]

[loaded] com.adobe.ARMDC.SMJobBlessHelper.plist (2016-05-14) [Support]

[loaded] com.adobe.fpsaud.plist (2016-05-09) [Support]

[loaded] com.google.keystone.daemon.plist (2016-03-03) [Support]

[loaded] com.lacie.LaCieDesktopManagerDaemon.plist (2014-04-30) [Support]

[not loaded] com.logmein.logmeinserver.plist (2015-03-27) [Support]

[loaded] com.logmein.raupdate.plist (2015-03-27) [Support]

[loaded] com.oracle.java.Helper-Tool.plist (2014-04-12) [Support]

[loaded] com.prosofteng.KXInstaller.plist (2014-02-17) [Support]

[loaded] com.teamviewer.Helper.plist (2015-02-27) [Support]

[not loaded] com.teamviewer.teamviewer_service.plist (2015-03-20) [Support]

User Launch Agents:ⓘ

[loaded] com.citrixonline.GoToMeeting.G2MUpdate.plist (2015-06-23) [Support]

[running] com.spotify.webhelper.plist (2016-06-11) [Support]

User Login Items:ⓘ

Skype Application (/Applications/Skype.app)

ElementsAutoAnalyzer Application (/Applications/Adobe Elements 11 Organizer.app/Contents/ElementsAutoAnalyzer.app)

Spotify Application Hidden (/Applications/Spotify.app)

Other Apps:ⓘ

[running] com.adobe.ElementsAutoAnalyzer.93472

[running] com.etresoft.EtreCheck.305312

[running] com.skype.skype.70432

[running] com.spotify.client.173152

[loaded] 399 Apple tasks

[running] 205 Apple tasks

Internet Plug-ins:ⓘ

o1dbrowserplugin: 5.41.3.0 - SDK 10.8 (2015-12-11) [Support]

Default Browser: 601 - SDK 10.11 (2016-05-25)

OfficeLiveBrowserPlugin: 12.3.6 (2014-01-07) [Support]

AdobeAAMDetect: AdobeAAMDetect 1.0.0.0 - SDK 10.6 (2016-03-24) [Support]

FlashPlayer-10.6: 21.0.0.242 - SDK 10.6 (2016-05-14) [Support]

AdobePDFViewerNPAPI: 15.016.20045 - SDK 10.11 (2016-06-03) [Support]

Silverlight: 5.1.10411.0 - SDK 10.6 (2014-03-04) [Support]

QuickTime Plugin: 7.7.3 (2016-05-25)

Flash Player: 21.0.0.242 - SDK 10.6 (2016-05-14) [Support]

googletalkbrowserplugin: 5.41.3.0 - SDK 10.8 (2015-12-11) [Support]

AdobePDFViewer: 15.016.20045 - SDK 10.11 (2016-06-03) [Support]

GarminGpsControl: 4.2.0.0 - SDK 10.8 (2014-03-31) [Support]

Scorch: Unknown - SDK 10.2 (2014-08-19) [Support]

JavaAppletPlugin: Java 8 Update 91 build 14 (2016-04-26) Check version

User internet Plug-ins:ⓘ

CitrixOnlineWebDeploymentPlugin: 1.0.105 (2013-04-26) [Support]

Google Earth Web Plug-in: 7.1 (2013-10-07) [Support]

3rd Party Preference Panes:ⓘ

Flash Player (2016-05-09) [Support]

Java (2016-04-26) [Support]

Paragon NTFS for Mac ® OS X (2015-09-02) [Support]

Time Machine:ⓘ

Mobile backups: OFF

Auto backup: YES

Volumes being backed up:

Macintosh HD: Disk size: 3.11 TB Disk used: 475.97 GB

Destinations:

Data [Network]

Total size: 3.00 TB

Total number of backups: 53

Oldest backup: 22/11/2015, 09:56

Last backup: 11/06/2016, 12:04

Size of backup disk: Adequate

Backup size 3.00 TB > (Disk used 475.97 GB X 3)

Top Processes by CPU:ⓘ

53% mds

20% com.apple.WebKit.Networking

12% mds_stores

9% com.apple.WebKit.WebContent

8% kernel_task

Top Processes by Memory:ⓘ

1.53 GB kernel_task

426 MB mds_stores

262 MB Spotify Helper(2)

229 MB mdworker(22)

229 MB Skype

Virtual Memory Information:ⓘ

27.00 GB Free RAM

5.37 GB Used RAM (1.50 GB Cached)

0 B Swap Used

Diagnostics Information:ⓘ

Jun 11, 2016, 12:44:54 PM Self test - passed

Jun 9, 2016, 07:30:08 AM ~/Library/Logs/DiagnosticReports/FinderSyncHelper_2016-06-09-073008_[redacted]. crash

com.lemkesoft.graphicconverter9.findersynchelper - /Applications/GraphicConverter 9.app/Contents/PlugIns/FinderSyncHelper.appex/Contents/MacOS/FinderSyncHelper

Jun 9, 2016, 06:29:45 AM ~/Library/Logs/DiagnosticReports/FinderSyncHelper_2016-06-09-062945_[redacted]. crash

Jun 8, 2016, 06:33:17 PM ~/Library/Logs/DiagnosticReports/FinderSyncHelper_2016-06-08-183317_[redacted]. crash

Jun 8, 2016, 06:14:26 PM ~/Library/Logs/DiagnosticReports/FinderSyncHelper_2016-06-08-181426_[redacted]. crash