Hi! I have a 20 gallon planted tank with a school of rasbora hets, a female betta, and a mystery snail. This tank is well established, coming up on its one year anniversary. I have had the rasboras since Christmas time. Anyway, just recently I noticed one of the rasboras was not schooling with the others, which I thought was odd, so I looked closer and I saw redness and swelling around one of the gills. The abdomen appears to be slightly swollen as well. Pics attached. Any idea what I’m dealing with here? Thanks in advance.