Them floro's should be ok while they're young, how far away from the plants do you have them?

I'm not sure if a mh will have much if any impact on yield over a hps. MH seems preferable as it gives tighter nodes and keeps the plant shorter.

Oh and a 250w hps for flowering an area of 8.25 sq ft is pretty low, you'll get around 3300 lumens per sq ft. I'd get at least a 400 watter or probably a 600.