Hey, new here. Just had a question. I’ve been gone away for a couple weeks, I have 4 RBP, in a 75g tank. So I came home today and one of my guys has a nibble on his lip missing. Just a nibble. And one of the other piranha is chasing him around relentlessly. They stop when I go near the tank, but when I leave the one chases the other around nonstop. Should I be concerned?