Suggestions:

-Get a bigger space OR only grow 1 or 2 plants in that space. I don't know what you plant to do with that MV bulb, but you ain't gonna get shit with it.
-More light! What you have there is not near enough for the amount of plants you have. To get a decent yeild, you want a min. of 50W per.sq.ft. So for 2 plants in that space, I'd go for 200W. You can use CFL's, they work amazingly well for veg, but when you hit flowering, things are going to move very slow.
-Turn that CFL bulb sideways instead of it pointing down. There is 25% more light output coming from the side rather than the bottom. We all know, more light=bigger buds.

This is what I would do, all in a nutshell. I would keep that space, grow only 2 plants, get more bulbs, min of 100-150W CFL's.

OR, get a bigger space, more bulbs, I suggest an HPS bulb for flowering. Hope this helps.

As for your leaves yellowing already, have you been giving it ferts at all?