Mooshee I think i pasted this in another thread for you but heres a good resource: Grow Marijuana FAQ, Cannabis cultivation - marijuana growing tips & photos and Grow Marijuana FAQ, Cannabis cultivation - marijuana growing tips & photos

The former has a key and pictures, the latter just pictures. It could be heat, nutes, deficiencies, any number of things, but go thru the key and if you're still not sure go to the plant problems section