Has anyone ever heard of a neon tetra nipping the fins off of a bunch of cories?? All I have in my tank are some cories, some neons, and then some guppy fry. It is possible that the two cories that died last night (both with very nipped fins) already had their fins nipped when I bought them, but the other four in there are staying so elusive and I never see them, so I am wondering if there is some form of bullying going on??