Jaws777, that tetra parasite guard, Is it albendazole or piperazine? I have fought the Godzilla of internal parasites, Callamanus, and won with no loss of fish life. I used goat wormer, flubendazole, to treat that particular baddie.
Parasite guard is a good choice. Sds will eat poop so maybe got it from ur other fish. Other fish seem ok? It will treat both internal and external parasites. It contains praziquantel, metronidazole, acriflavin, and diflubenzuron. A good mix of meds.