I have two gymnothorax tile in a brackish tank. One I've have for over six months, the other I bought less than a week ago. The new one must have come from the lfs with Holeinthehead because I saw a dot on her forehead, but just thought she bumped it in the transferring process. now it's obvious that she is sick. She has one confirmed hole above her right eye, and one beginning on the left. I did a 50% water change, but should I treat with anything?