First of all, you're pretty early in the flowering stage to worry about big buds... they will fatten up tremendously over the next weeks. One thing I would tell you to do to avoid any problems and to help your girls is to cut the Grow Big way down now... I've used Fox Farm and Grow Big was always giving me lots of problems - nute lockout, nitrogen toxicity... and in the flowering stage plants don't need or want a lot of nitrogen. Cut Grow Big in half and triple the Big Bloom and double the Tiger Bloom.... make sure your pH is sitting around 6.2 and then just be patient! They look great!
Good luck!