I have 9 Long finned black skirt tetra's, two of them have white dots on their back fins only. I started heat treatment by slowly raising the temp to 86, it's been there for over two weeks with no change. They don't seem lethargic or sick in anyway, they are eating normal. I've been doing water changes with vacuuming, It really hasn't changed at all and they don't seem to be bother by it. I had them with some fin nipping fish a few weeks ago, could this just be scar like tissue or something?