i'd prefer to have the pH between around 6.3-6.5... solubility of everything is pretty on point at that range. The night temps are probably like 65ish... but that has little to do with the color. they're just out of food, at the end of their cycle, and the pH is inhibiting them because it's like 6.9ish.
i actually defoliated those confidential cheese plants pretty heavily around the 21 day mark... and one week later they looked not much different than they do now in terms of foliage amount. I definitely agree some defoliation is necessary, especially for air flow with a really leafy strain like this confidential cheese. but defo has to be done at the right times throughout the grow. if you go back about 4 or 5 pages you can see those plants at 21 days, and how they were defoliated, and then what they looked like a week later. this strain just grows the leaves lol. you should see the confidential cheese when it doesn't get a good defoliation... holy crap it's a mess! This was actually a pretty good run in terms of the amount of foliage I like... just not a good run in terms of soil pH (neither were the last few LOL). I'm working on it though. more to come on my thoughts on that another day. Have too much homework this week to get into those philosophies hahaha.