Are you feeding them the proper size of feeder? My ball came with mice and I continued for some time (she ate them easily and balked at the first rat I tried) but I got her switched to rats and now she's a great, properly plump girl. It made a big difference, even when I spaced her feedings out a bit longer (and kept her on white rodents - don't know what her problem is with any other coloring!). Next up is my boa (move her to bigger feeders) but I'm not sure if she's big enough to go to rats yet as I don't like to rush things. I would sooner that my snakes eat smaller items than to scare them off eating with rats that are too big.