a hospital tank is nice....but...
IF it's ich, removing the fish for treatment won't solve the problem as the ich lives in the water column, and subrates as well.
IF no plants are present, raise temp to speed cycle of ich, add salt and wait. Then do large water change, and repeat. After about 4 days, I usually don't have any problems left.
Look to the cause. Ich rarely goes after happy healthy fish. But loves stressed ones in my experience....unless I added a new fish without quarantine first.