Okay so im no master weed jedi either, but if i had my guess i would say that your leaves are fine... your plants are sucking up every ounce of nitrogen to produce more buds, causing the leafs to yellow. They look like they're far enough in for the buds to be able to photosynthesize on their own, so trimming down some of the fan leaves is an option.

Other than that the cola's on your plant are massive, and if you really are only 4 weeks in, thats a damn good strain for them to look that meaty. I wouldn't be too worried, just make sure you keep them well fed and well lighted, and you should be golden!:rastasmoke: