My fish are getting white sports on them, Can someone please help?

Hey everyone. I got new oscars from a pet store the other day, and I noticed they have tiny white spots on them. I do not know what that might be so I hope someone out there can help me. First it was the oscars, and then most of my fish started to get them. They tend to swim kind of sideways at times because of that, well at least they never swam sideways before. I have many different species of fish in my tank (pacu, oscar, pea b, dotted b, dinosaur eel, crayfish, small frog, algae eaters, berch, 1 goldfish that never was eaten, 1 brown hoplo, and last, silver mollies. The fish eat fine, it seems like they can't stop eating. I change my water regularly and it looks very clear. If someone knows the answer to my question, please help.