overheated

Hello growers, Recently I've noticed some color changes and burnt aspect on my bottom leafs. I took some photos so you can help my identify the problem and fix it. Is it caused by overheat? Thank you all in advance.

Yo is there any experienced growers that can tell me how too save my girl she's 4 weeks into flower under 650 watt hps. Have turned light down too 400 too reduce heat .Lots of the leaves on the plant have crisped up and curling up going brown and dieing. Can my plant be saved ? How can I revive...