week 4 of flowering leaves falling off?

i am in week 4 of flowering and for some reason some of the realy big fan leaves are turning a lime yellowish color and falling off but the new leaves and groth seem too be ok. is this normal?

anyone?????

yep its normal for flowering

ok cool ty for the info, someone was trying too say that there was gnats in my soil eating away my roots lol.

man i hate thows buggers made me harvest early last grow but if it were knats everytime u water ull see them or by just looking it your grow space ull see them playing in the soil