[Redshrimp2709]

So my black phantom tetra has this blisters on the mouth and one of it's fins. It looks like just an air pocket underneath a thin layer of stretched skin. I have no idea what this is. Any help from the aquatic community would be awesome! I'm wondering if I have to place this fish in a container with antibiotics for disinfection.

The said tetra is behaving normally and eating, showing no signs that it even notices what is going on with her.

Water parameters:

90G softwater community set up (mostly South American)

pH: 6.4
Ammonia & Nitrites: 0 ppm
Nitrates: 15 ppm
CO2 injection

water is stable with regular weekly water changes. Everything else is thriving.