i no what u got its called ph trouble i my opinion i dont think its heat stress his light aint strong enoff for heat stress being its out in a open room ,,but any ways i think its a ph problem so my advise is to get a ph up down kit if u dont got one if u do and u have adjusted ur ph then i dont no ,,but if u look at my first grow ull see in the first page of picks my bottom leafs were doin what ur are doin and i took someones advise on hear and got me a ph kit and its doin great ever since ive had no problems since but any way bro i wish u luck hope all works out for u and no matter what it is u cant loss by getting a ph tester and the kit cause if u plan on growing for a little while u will need one for shure so if u take my advise u cant loss no matter what cause need one to grow any ways ,,unless u got one ,,peace
HAPPY GROWIN TOM TOM
AND HAPPY NEW YEAR