Echinecea is good. Just use it sparingly or they will develop a tolerance for it.

You can get Tylan at the feed store too as it works on Myco-related illnesses. It is bitter so you have to really dilute it in the water.

I wouldn't resort to that unless you have mice you really like. If they are still poorly after a few days to a week, then just feed them off. You don't want mice with bad immune systems making up your colony.