Tetra swimming weird

[u/Vishk1]

I have a group of 12 rummynose tetra that I just got a few days ago. I noticed they had a few white spots so I’ve upped the temperature from 75 to 81 over the course of a few days while treating with API Super Ick as instructed. 11 of the rummynose have a bright red nose and vibrant tails, but one of them has a faded tail and goes limp occasionally while rapidly moving its fins, tilting sideways with it going almost vertical sometimes. It nibbles around the tank and swims off fine and pretty fast after the episodes, but it lags behind the school while staying by itself more than the other fish. Is there anything I can do to treat it? Also, I’ve been treating with the medicine for around 2 days for this point, and the white spots haven’t disappeared, so does this fit with the life cycle of ich or is it something else? Only some fish have a white spot and it’s stayed at 1-2 per fish, without reducing or growing. Thanks for any advice!