I'd have to say that's lacking a little nitrogen.
I'm assuming you're using nutes, most flowering nutes out there have a low level of nitrogen (N-P-K stands for levels of nitrogen [N]; phosphorous [P]; potassium [K]), which is what causes an overall light green color with yellowish fan leaves on the bottom. I'm just guessing from this blurry picture that your problem is low nitrogen. If the symptoms that I stated are indeed true, just add some vegging nutes (those are usually high in nitrogen) or any other nute that will give you nitrogen.
323cheezy is right that it's not too big of a deal to lack nitrogen in later stages of flowering, but there's nothing wrong with fixing the problem either. Happy growing!