How long have they been in there? How long has the tank been established?
My
GBR didn't eat and didn't look too happy for about three days, now he's fine. He was apparently just acclimating to new surroundings. Eventually he scooted up to the top and now he eats just fine.
It could be that the water isn't 'old' enough and it's causing the little guys stress.
Good luck with this gorgeous fish!