About 2 weeks ago I noticed a big white bump on the mouth of one of my Chromis fish, it is slowly getting bigger. I have 4 other Chromis that are completely fine, no signs of this on them. I have tried to do research to find out what it might be - thought maybe a parasite but it looks like it is under the skin. I did a freshwater dip to see if it would fall off if it was a parasite, but this did not work. He is eating and swimming around (but kind of stays in the corner a lot swimming at a 45 degree angle). I'm worried about what this is. Has anyone seen anything like it?