I second Mebbid on the advice. Use heat to treat Ick. I believe that you lose less fish that way and the majority that remain will be healthier for not being medicated. Some losses may have happened anyway - don't blame the heat. Do increase water surface agitation whilst at a higher temp as the water holds less oxygen. Dropping the tank level so filter outlets splash into the tank is a good way. Do wait a week after all signs of Ick have gone to ensure the Ick cycle had been destroyed.
I learned my lesson when I added fish straight into my display tank so please do quarantine all new fish for a couple of weeks - in particular, multi-chain fish shops seem to be rife with it.