red minor

Hey, so one of my eight serpae tetras has looked a little more pale and ragged than the rest of my serpaes for a while now, and I noticed today that it was going after the food aggressively but would spit it out immediately after trying to eat it. I used the flake food that I give to my serpaes...

My Serpae (or red minor tetras) seem to have white spots on them but each only seems to have one on their mouth or near there. Could someone identify if it is a disease or if it needs to be treated at all?  Tank size: 55 gallons pH: 7.0 ammonia: 0 nitrite: 0 nitrate: 0 tank temp: 74 Degrees...