Sometimes what goes on in the tank you are observing will effect the fish in the isolation tank. i.e. dropping medicine mare cure the fish there, and dropping food will feed it.

HOWEVER, dropping vitamins does not affect the fish in the isolation tank.

In a new tank I had a twin pair of golden goldbulbs who were both in the red zone after leaving the game on 2x speed overnight by mistake...

I put one in the isolation tank and bought vitamins to observe the effect. And nothing happened to it, but the other fish in the main tank improved to the yellow zone (after all three doses...)

After putting the fish back in the main tank and buying (and using) another three doses of vitamins, it improved to the yellow zone and the other fish improved to the green zone.

Just thought that people would like to know...