This is my first grow and I started plants into flower in cfl, made them purposefully small. Switched them to 400w hps a week into flower. They are now getting on to their 5'th week with 3 or so left. I've fed them nutes once in veg, never again. The soil is a organic blend amended with ewc and fungi. My ph in has always been 6.5-7.0, and runoff measures good too. I do have "heat" issues; since I grow in a garage I get to 101F on 99F days, but the heat has been worse in the past for longer and had no issues. I dump a lot of outside air which I think is helping. I'm wondering if this is just normal or if I have a nute deficiency starting? The first two pics are of a sicker plant, and the third is of another plant starting to show it on the bottom fan leaves more but overall the lush green they had has disappeared.
Leaves tend to yellow during the last weeks of flowering, it looks fine. Maybe add some nitrogen if you're really worried but I think you'll be okay.
Id just get some molasses and water. Sprinkle some Bat guano and worm castings on the top and water over it. Also add a 1/4 tablespoon of Epsom Salts. When you water make sure the top is dry before you water. 99% sure with those size pots you should water every 3-5 days. Remember to not water 4 days before harvest