I think you should feed them what they will eat at this size. They aren't old enough and don't have enough weight on them to fast right now. Sometimes they just don't like larger prey. Ease them up to size but make sure they are eating... I had to drop prey size for one of mine until he was eating well. Then I bumped to a more appropriate size and he did just fine. I'm sure there are diff opinions on this. This is just my 2 cents..