I recently purchased two True Percula clownfish. The other day I noticed that the skin near the entrance to the fish's gills appears to be pulled and stretched out. There is also some pinkness observed on the skin. It is located on the white band near the fish's head. The injured fish and the other clown have been nipping at each other and I think it may have been caused by injury. My nitrate was very high (50+) for the first week I had the fish. I have brought that level down to 30 and installed a protein skimmer a week ago. I am wondering if there is anything I can do to help the injury heal.