Thanks Naomi! I'm 99.99% positive this isn't a protozoan (ich/brook etc) based on research that hypo should kill such. Hypo doesn't work for worms. So I'm left to conclude that is all it could be, but there isn't much authoritative on the net about these. There are some good threads out there though.
Anyway, per WWM the chance of a worm that attacks multiple species of fishes is very low, so I don't know if this could be the explanation. Anyone else have thoughts?