Fungus gnats or am I tripping?

Don't worry man it's senescence. End of its life. You should be flushing now. Lovely purple buds pal

Your plants look fine. Don't worry about it. Looks like you're on the home stretch anyways. The leaves will start to die off regardless as your plant uses up everything. However you can rule out fungus knats. If you would like, buy some cheap yellow sticky traps. That will tell you if you have a knat problem and how severe it is.

It could be a factor of thing nutrients or even ph , def check ph run off and see what happens but with it being the end might just let it run it’s corse

Not fungus gnats, that's for sure. Looks like she might be starving for potassium if this is the plant from your Purple Kush CBD diary. Could also be bad pH, over watering, bad fertilizing program etc. You seem quite close to harvest and I highly doubt anything you might do to try and "fix" these issues would have any effect before you are ready to chop. Asking this question 2-4 weeks ago, when it probably first appeared, may have given enough time to do something positive.