One of my bleeding heart tetras looks unusual. The best way to
describe it is that it looks "puffed up". It seems to be swimming
perfectly fine and there doesnt seem to be any other symptoms (it might
be breathing a bit more rapidly than the other fishes)

I can't remember the name of a fish disease that has this symptom. Can
anyone help??

THe tank specifics a
-55 gallons
-PH 7.5
-temp 76f
-ammonia 0
-Nitrite 0
-Nitrate 20-25 ppm

No other fishes are currently showing any symptoms. Stock includes:
-1 dwarf pleco
-2 gold algae eaters
-3 Yoyo botias
-2 lemon tetras
-3 black phantom tetras
-4 bleeding heart tetras
-5 zebra danios

Any info is appreciated. Tanks.