frozen krill isnt bad for them but they really should have a more balanced diet, just as with people only eating one type of food isnt the best, i would fast them for a day and then soak some pellets in the tank water with the krill and give them the pellets first, the more variety you feed them when they are young the better and the less picky they will be as adults, its much easier to get juvies onto pellets than it is grown adults who are set in their ways, but yeah try to get them on a cichlid pellet and then feed the other stuff as treats
