i would stop the treatment, ..but thats just me....im not much into adding chemical to the tank
in all honesty, i think your clowns probably just had a weak immune system and your chromis didnt....did all the fish all have ick?....or just the clowns?.....did they ever start to eat?.....i know that in my tank, anytime i add a new fish, the new fish always show some sign of ick the first couple days (never on the current fish).......and i just feed teeny tiny amounts of food through out the first couple days and every couple hours......if they start eating like pigs, they'll turn out fine ....but thats in my tank, and it works for me........im sure i have ick living in my tank too but all of my fish are healthy enough to fight it off....your chromis was probably able to fight it off
i say, for your best bet,...purchase your next fish from a fellow reefer...atleast you'll know that the fish were from a healthy tank....not saying that our LFS dont have healthy animals....its just that they go through a ton of fish....and more than likely they were still stressed from the transition to the store, and in the store when they are chased around by fish nets all day long..and then some more when you took them home