If you have many small bass they tend to eat all of the forage base that can fit in their mouths. The BG that are too big for them to eat grow even bigger because they do not have the competition for their food supply from their smaller cousins that the bass are eating up. I am dealing with a similar problem in my newly purchased pond. After 4 months of culling any bass under 11 inches I am already seeing some minor improvement in the weights of the 12 inch and larger fish. I think I am on the right track but realize it will take time.