Ich is very hard to conquer and cure, once it falls of the fish it lives in the gravel and stays there until it multiplies and gets strong enough to attack the fish again... keep temperature high and try the Maracyn. The trick is trying to treat them with Maracyn and once you're done with the treatment, immediately siphon the gravel thoroughly as much as you can to try and get the ich out of the rocks. Hope this helps, it might sound stupid but I had the same problem and I felt all hope was lost, but going to the lfs helps a lot getting all the guys different inputs and different options helps.