Looks like brook. I had an outbreak short while back lost a lot of fish. First to die was my clowns. Is the fish swimming on top at the waterlevel? Unfortunately there is no propper cure that will save the fish. Tank should run fishless for about 4 to 6 weeks for the parasite to die as keeping a fish in the tank the parasite has a host and may pop up again when least expecting it. Fish can live with brook for years and just one day show symptoms.