It could be the tin foil. Tin foil concentrates lights into hot spots. This will cause your plant to become stressed out man. And it can eventually kill it.

What kind of lights you using? Whats the temperature in your grow space?

It could also be high humidity instead of over watering. Some strains of cannabis dont like high himidity. So if you use a spray bottle or anything, stop. Go up to like homedepot or a flower nursery and grab a cheap himidity meter. If its higher than 65% its most likely way too high. Anything below that is usually fine.
GRB.4.Life Reviewed by GRB.4.Life on . MY LEAVES ARE CURLING UP! MY LEAVES ON MY PLANTS ARE CURLING UPWARDS TOWARDS THELIGHT? IS THIS GOOD OR BAD???? HELP PLEASE THANKKS! Rating: 5