What's wrong with my Columbian Sharks' skin?

So here's the deal. My boyfriend bought two columbian sharks. One is about 7 inches long and the onther one was about 2 1/2 inches in length. About three days ago the big one got a cloudy film over its eyes and little tinky white spots. It looks like ick. The smaller one got the spots to and then started swimming funny and died. There are two cichilds in the tank also and they have no symtoms of anything. We are treating for ick but I'm not sure that's the problem since not all the fish are sick. Is there some reason that only the sharks would be getting ick and not the other fish or do we have a different problem on our hands here? Any help would be appreciated. Thanks!