I don't think it's the cold at all, dude!!! I'm not sure what it is, but not the cold. The reason I say this is because my plants do the same thing and my temps are perfect for day and night.
I have a question, do those leaves have very much THC produced on them? Do some of the leaves have round tips instead of pointy? I noticed you seem to have cut the tips off. And, does this happen to every cola, or just some of them???
I personally think that it's heat. I notice that the colas on my plants that are effected like this are only the ones that are closest to the lights. The ones that are farther away don't have the same problem.
Anyways, I look forward to your responses to my questions. Maybe between the two of us we can figure this out for us both!!!
-S