I just recently added a beautiful Royal Blue Tang to my 20 gallon tank as a friend to my Clown Fish. She’s been fine for the past couple of weeks, but now she’s breathing hard, trying to swim and laying on the bottom. It looks like she has something like a “film” that you could peel off of her bottom half of her. I know it sounds weird, but is this possible? Is there anything I can do to help her?