in my novice experience that looks like 1 of 2 things, they need more humidity and are over heatin OR it's a nute burn....so I dont know if that helps but to let you know I keep my humidity in the 50+% area....infact right now my room is @ 76.6F and 54% as long as you keep your humidity above 40% BUT if I am wrong and this is a big BUT could someone pls correct me, I hope this helps!