What is causing this? Pics included

Hello all, my buddy is having some problems with his crops. Everything was looking great untill about 2 weeks ago when most went down hill. Recently his lights were switched to 18/6 from 24/0, so at night there is no heat now. He is in norcal and it did get pretty cold at night here about 2 weeks ago, does this look like temp issues? Some of the plants in the room seem fine. He feeds botanicare pro gro and liquid karma and calmag. Thanks for reading!

What’s his PH at and how often does he water?

how cold is it getting and, a 6 hour change in lighting all at one time may have been too much of a shock, better to cut it back slower. 22/2 for a few days, then 20/4, 18/6. Dramatic changes in anything can shock your plants.

His ph is about 6.5 so i dont think its that, and now that i think of it i only changed his lights about a week ago and there were probs before that. As for watering.. He slacks lol