Sounds like root rot is out then. The roots look excellent. Good!

Now let's see about the other. Night temps could be leaving you with dewfall. You'll want to start a treatment of Serenade to protect against various fungi that could attack your plants in the moist conditions. When you get home, would you mind trying to get pics of the worst-affected leaves, plus some that have only MILD symptoms (blotching but not wilt)? Try propping your phone or camera on a tripod or anything that won't move when you press the button. I want to see that damage pattern.

How is the health of the base of your main stem on the wilty plant? Do you see signs of damage/fungal infection?
Is that plant in a part of the room that does not get much air circulation?
How are you moving air within the chamber, apart from exhaust?
Where is your intake, and how large is it? Is it obstructed?
Good exhaust may solve your humidity problem. You really want to keep it below 50% at all times in flower or you will end up with rot.