Having installed either IOS 9.01 or 9.02 and since then you have had problems with "Connectivity" & or "Performance" (LAG) here are a few things to try:
Connectivity
1. Hard reset of device - Unlock device and then press and hold both the BACK BUTTON & the ON/OFF SWITCH at the same time the device with power off, KEEP holding these buttons until the "Apple" logo appears, the device will now reset and start up. NO DATA should be lost.
2. Remove your WiFi connection, go to "Settings" then "Wi-Fi" press the ⱷ icon and select "Forget This Network" when prompted select "Forget" Restart the device as per option 1
3. Set your device to have a static IP Address, Subnet Mask, Router & DNS. Leave Search Domains EMPTY, re-start device as per option 1
Performance (LAG)
1. Re-starting the device as per option 1 above. This may have corrected the problem, test to verify
2. Have you backed up your device via iTunes recently? If not, OOOPS! If yes, then you can perform a restore to an early version of the iOS
3. Backup the device but ensure you change the path within iTunes as to where you back up.
Within iTunes select your device then under preferences, advanced option change the location where it backups up. (Write this location down, you will need it later)
Call the folder iOS9 as a reference point. Backup the device.
Within Windows Explorer, select your device and then open the internal storage via explorer, you will see folders open each in turn and copy ALL your pictures to your PC, e.g. C:\IOSPictures\ this will allow you to put them back on to the device once you have restored it to an older version. (Only the missing ones)
If you backed up your device prior to installing iOS9> then you can skip this and just restore it back using the latest backup you have. (remember, if you have taken pictures or made any changes since this backup they will be lost)
Change the backup location back to the original location and restore the device. Once rebooted check the iOSx version and then copy back any picture from your PC
PLEASE Remember to ALWAYS backup your device before updating the iOS, just in-case... Whilst I hope the above helps, I do not take any responsibility for any lost of data, functionality of your device or ANY problems you may have after you have applied any or all of the above suggestion.
The above is supplied free of charge and as such are used at your on risk.