I'm not sure what's going on here but my trio of paroon sharks have come down with some sort of ailment..It started with just one of them a few days ago,it started to get a little pale in color and then white blotches appeared on its body and fins and now the other two are getting the same appearance.There are three small IT dats in the tank and I do about a fifty percent weekly water change.I have no idea what is wrong and I've never had to treat catfish before so I am not sure which medications are safe to try...