Problems with 4-week-old

Hello world! I have just noticed what seems to be "burn" patches on the first female I have spotted in my bunch. They are all about four weeks old. I have a 3x4x6 portable closet with a six bulb T5 light, CO2 tank. Temp is about 72F. 18/6 lighting. Yesterday I jumped my nutes up from about 200 to 900ppm. This is in response to the horrible water we have around here, which contains about 450ppm with a pH of 8.2. I purchased a faucet filter (not installed yet) and a regular pitcher filter. The pitcher took the pH down to about 6.7 and lowered the ppm to 370. When I finished mixing my nutes last night. I had just under 1200ppm and pH was at 5.7. I constantly read when I can. I just wanted to get some real life opinions on my crop. I think it could be 3 different things; Nitrogen, Phosphorous, or ventilation. Any input will be appreciated. And this is the only plant showing the patches.

im not sure but it may have been the jump of nutes.. might should have slowly should have brought them up.. But, not sure..

I was thinkin' that also. I have diluted the nutes some and lessened the feeding which is now 1 minute every 2 hours. I am on a drip system, but it acts like a flood and drain. I'll see how this goes. Thanks for your response Ace.

your plants are still looking pretty sweet though..

absolutely... Be proud of those! slowly bring up them nutes and I think it'd be fine, cuz that's a pretty big jump...