Saulosi problem

I just finished treating my tank for bloat. All of my fish are now eating, but I have a new issue. One of my saulosi is sitting on the bottom. It is barely using it's fins near its gills. The area where the fin meets the body looks red. While it sits on the bottom, it keeps its fins tight to its body. (I say its because I don't know if it is male or female). It can swim and does, but mostly only uses one of these fins. It was perfectly fine this morning. I just tested my water and ammonia and nitrite are 0, nitrate 10 and ph is 8. Right now, it is rubbing its face on the rocks. What causes this and what can I do to help?