If it's the bottom leaves, and if the plant is...ehh...around a foot tall, I wouldn't even think twice about it, you're fine. It could be a multitude of things. IMO I think that the CFLs that i'm using aren't penetrating far enough, and those leaves are just dying, so the plant gives those leaves bottom priority compared to the top ones getting the most light. If you're really that concerned you could mix in some nitrogen rich nutes in with your flowering nutes but I don't feel that's really necessary. Leaves will die, dying is inevitable, just gotta make sure the new leaves/buds look fine.