Sick fish

Had to set up an emergency fish hospital tonight in my spare tank.

I have had a recurrence of the fungal infection that killed off most of my fish earlier in the year. Very frustrating, I have done everything I can to eradicate it. The two fish left in the big tank must be resistant, they have never shown any symptoms. Are they the piscine equivalent of Typhoid Mary?

This poor little guy doesn't look too good, sorry to say I think he might be belly up in the morning.