About a month ago my female Betta, Amelia, developed a small white patch near the front of her dorsal fin. I had thought it might be fungus so I treated her water with Melafix for a week and thought nothing more of it. Well, recently (within the past week or so) I've noticed the spot getting bigger and spreading slightly. It also looks as if she has lost some scales in that area and the patch has now turned more of a pale pinkish color towards the center. She still swims around and eats normally (she's quite the pig actually), but this thing has has me worried. If you have any ideas of what it might be, or how to treat it, please do reply.
She is currently kept in a heated 10 gallon with 4 other female Betta fish. I change 25-50% of the water every week depending on the ammonia level.
And sorry the pictures are not of the best quality. You can't exactly tell a fish to sit (swim?) still.