I think I have my solution. The girls don't like the betta food but they DO really like blood worms. So I'm feeding everyone the tropical food, which the bettas take a bite or two of. Then while the tropical trio are scoring the rocks for dropped food I sprinkle some blood worms right in the faces of the bettas, who eagerly scarf them up. I've also seen them eating some of the cory's shrimp pellet. So I'm guessing they're getting their protein.Ugh Stupid fish. The bettas dove for the sinking tropical pellets while the others played with the bettas pellets at the surface.