Hey, bigger pots would help if that's possible. 4 gallon is recommendable, which is what we have used. Although if anything bigger than what you have is better.
It would be a number of factors that contribute to bud size.
-Ferts used
-Ventilation, CO2 replenishment, air flow
-Strain (some naturally produce bigger buds)
-Lumans of your lamp and distance.

I don't really know enough to be giving advise on growing (I'm usually the one taking it!), so take this with a pinch of salt as I could be totally wrong.