Hey Chad,
Well this one is easy..... You are overwatering. I can tell by a couple ways. First your bottom leafs are falling off. Secondly all the leafs are curling inward, they do this in effort to create as much surface area as possible to allow the stomata to expell excess water. I would bet that your plant looks "thirsty" alot, therefore you water it. A plant being overwatered shows very similar symptoms as a underwatered plant.
With that said unless you bought the "organic" kind, M.G. soil is not good for ganja. It has harsh synthetic nutes. Also you will need ALOT more light. If you want to stay with CFL, Home Depot sells a 300w equivelant bulb (basically a spiral T5) for $9, Install alot more light! Finally you NEED to install a fan in there. Intake and outtake with PC fans would help alot to. A fan blowing indirectly in there would force the plant to loose water at a more rapid, but safe pace. I assume this is your first grow. I would personally recommend Jorge Cervantes "Marijuana Horticulture: Indoor and Outdoor Medical Growers Bible." Im not advertising for it, just recommending it. Full color, and goes into great detail the basics you should know. Also check out the GrowFAQs, there is a link at the top for it labeled "FAQ."
Good luck, take my advice and it will do alot better. Your container size is perfect for the life of the grow.
-BlessAmerica
PS if it were nute burn you leafs would all be rusty and crispy, not yellow. Also once you get the overwatering taken care of add some Fish emulsion (pure Nitrogen 5-1-1) to your water to help stop that yellowing. Good Luck!