I dont mean to be an arse or anything but have you tried freshwater dipping any of your fish. If not, buffer some similar temp and pH freshwater in a bucket, catch your fish with "bad" ick, and drop them in the freshwater for about 1 min, then grab them with your hand and scrub the crap out of them with a soft bristled toothbrush, then drop them back in the freshwater for another couple mins, or untill they breath very very laboured, then drop them back in your tank. May seem alittle harsh but having a dead fish is much harsher in my eyes, would you rather have some roadrash, or be dead??? This method has worked very very well for me and I have done it more than a few times.