I had a case a couple years ago that wouldn't react to any medication I tried. I found an old aquatic microbiology book that said ich cannot live at a salt content of 3ppm or higher. If you can get your hands on a salinity moniter, make sure it is at least 3ppm, 2.5 is not enough to irradicate. I also raised the temp to 90'F with tons of aeration, and the ich went away and so far, hasn't been back.
Since seawater is @ 35ppm salinity, most cichlids will tolerate 3 without even flinching.
Since seawater is @ 35ppm salinity, most cichlids will tolerate 3 without even flinching.