I presume the Cherub is small and the Clowns some larger. It really should make little difference, though. The Angel is still getting used to the new surroundings and should compete for her meal as she adjusts. You might try putting food in different areas so at least they won't be competing for the same flakes.
It is good to keep the Cherub well fed; mine has never bothered polyps or anything but there have been some reported to munch on forbidden fruits. You might also put in some frozen brine; thawed with a bit of Selcon, for diet variety for all the fish. IMHO, they are the "safest" of the angels but nothing is certain.
My
Ocellaris pair were still growing juveniles when I added the Cherub (
Centropyge argi) nearly two years ago. My Cherub is still a bit more shy when approaching the tank than the clowns but certainly not slow at feeding time!! These fish get along very well with no conflicts.
BTW, all C. argi's are born female. In a pair relationship, one may change gender to male, just the opposite of A. percula or A. ocellaris.
HTH
Dick
