My Flame Angel has a small area on his top fin that is white. It almost appears as though a small piece of his fin is missing. He's eating well, grazing on the rock, swimming in and out of the caves etc. Could it be wear and tear from squeezing through crevis'? Everyone else is doing well. I first noticed this a few days ago. It doesn't appear to be enlarging/spreading. Water parameters are all good - I checked this morning. I wonder if a tank mate nipped him. Everyone seems to be getting along well when the lights are on though. Tank mates include Purple Tang, Flame Hawkfish, 2 Perc. clowns, orchid dotybach and 4 Bl/Gr Chromis. Everyone is a juvenile in this 90 gal. tank. Any Clues?