Only a few weeks left but I am having problems!!

So I have been dealing with issues with these plants for a while. Everything was finally going fine when they started exhibiting other signs. The bottom older leaves are turning yellow and eventually dropping, and now the middle and some of the upper leaves are turning brown on the edges and curling up at their tips. They are on a 12/ 12 schedule and should be within three weeks of harvest. I am giving them an appropriate nutrient mixture but have started to think the ph is off in the water and preventing the nutrients from working. The pics show the entire setup, close up of young bud, curling tips of middle leaves, and discoloration of leaves. Thanks for any help, I really want these guys to make it.

yellowing in last few weeks is normal, stop feeding 2 weeks b 4 harvest, mayb halt t spoon epson salts in a gallon of water may help with leaf curl but you r so close i think thigs will b fine. its normal to worry a bit.

Perfectly normal. Most annuals vegetation suffers when fruiting occurs, usually manifesting itself in yellowing and eventual dying off of older, already-drained of it's purpose, foliage.
Now is not the time to try to fix something that really isn't an issue. I thought the same re: base pH . . . so I started pH'ing my H20, which caused other, worse looking, problems. I went back to normal, and things are as expected.