Gah im late, but whatever I will join along for the funsies!! I have pulled a few harvests now from pc boxs/small cabs and what it looks like is that there may be some heat issues combined with overwatering/nute burn.
From what I can see in the pictures you have posted the highest exhaust fan is about 1/3 to 1/2 way up the case (If im missing an exhaust fan somewh, which is the glaring issue here. The hottest air in your growpro is located at the top which means you aren't actually exhausting the warmest air in your case and if anything are probably pulling the warm air down onto your plants more. This will stress your plants out, making them more susceptible to other ailments, especially if those have to do with the water content of the system (your plants roots/soil).
When the plant gets too hot it will adjust the small openings in its leaves to compensate for the heat by essentially sweating. So if you are giving the plant nutes and water during this heat stressed period you are actually furthering the stress caused on the plant because it was trying to self regulate and then the system it was now getting used to gets changed. It really is a vicious cycle until the heat problems are solved.
So now what needs to be done? First of all at this point in the grow your plants really dont have time to recover properly so now its on to damage control, so I would shut the lights off completely regardless of what you see in terms of trich color unfortunately. As of me writing this its been about 80 days of flowering which is a long time so your plants are likely done maturing anyways. If you want to try something to increase the potency you can try leaving them in the mrgropro with the lights off for 12-48 hours (keep fans running at least a few hours a day).
This darkness will do a few things for you: 1) your plants will freak out and think the world ended, which will make them put all of their energy left into producing bud (because they are trying to get laid obviously) 2) Light actually degrades trichomes and THC (the plants make them to to absorb light damage) so in combination with #1 you will get some more potency out of this round and finally 3) it will start your drying and curing process (dont give them anymore water just turn the lights off).
Sorry for the wall but I hope this helps!
tldr; put an exhaust fan higher up in the case, your plants are probably fully mature (think about harvest or darkness period)