Hello,
I recently bought several yellow Chromis, they picked on each other till I had but one! The one left has doubled its size and every once in a while picks on some of the smaller fish in the tank. My Flameback angel chases it once in a while too. I think only the green and blue Chromis are truly peaceful. I should have guessed this might happen as I noticed some minor chasing in the tank at the LFS. So,my advise is watch the fish in the tank, if there is some chasing or picking going on it will also happen in your tank if you bring them home.