I just got back from a trip and I noticed that my adult size clown fish is missing his tail. He just has a tiny bit where the body makes a "U" if you follow his back. I am also missing the smaller clown fish. Another thing I have been noticing a few days before I left is that the tangs have torn fins. I recently added some new rock, but I started to notice these before the rock was put in. Could I have a predator in the tank? Could this be caused by my carpet anemone? Also the blue tang has a white patch on his side about a 1/4" round.