Once they settle in they will become more confident and come up for food. what flake food are you offering them? They may not be keen on the food. and I would agree to feed them smaller amounts.. but I would also feed them more often. Finding a balance between maintaining proper water quality, and a growing fish. Young angels can also be finicky eaters. You can also try frozen brine, and bloodworms. one of my personal favorite flakes for carnivourous fish is Ocean Nutritions prime reef. My Angels love it along with a high quality flake staple, frozen foods, and the occasional treat of baby guppies (They are 2 very large adult angels)