Hi,
If they are new fish and you already had them in the main tank, to qt and treat them is not exactly the best way to treat these newly acquired fish.
What are you treating for? Just an observation but Odds are anything they had is already in your main tank, so it would probably be best to treat all the fish together now, in that tank.
Can you post more info about these fish, how long you have had them, what you are treating for etc.
hth,
al