I own 7 Bala's in two different tanks, and I don't worry too much about their diet. They all get along fine, although I never see them eat anything but flakes. They never go for any live food or Cichlid Pellets, although on occasion I have seen them hunt down a Sinking Shrimp Pellet.
I have always been very critical of people who tell others to move their fish into a larger tank. You have a 55 Gallon Tank, so I assume it is 48 inches long. With 3 Balas, 1 Pleco, and 3 Giant Danios, You have plenty of room. If anything, add 3 more Balas to create a better school and establish the Balas as the dominant species and the Danios as the dithers.