Do you have a big airstone in your tank? (Its a blue strip that causes bubbles in your tank when plugged into an air pump.) I only ask because anytime heat is turned up in a tank, the fish require proper aeration, because heat takes more oxygen, so your fish may become lethargic if they are having trouble breathing properly :/
And yeah, the tricky thing about Ich is that once you notice the spots are gone, and you think it's over, that's actually the PRIME time to treat because that is the parasite jumping off the host and falling to the gravel, where it triples in reproduction, and can affect and fatally kill your whole tank! Don't give up hope! I once had to treat Ich for an entire month! Lost one of my favorite Mollies, but it was worth having a working, peaceful tank afterward.