Trouble in the Tank! White Spot Disease?!?

[stealthspy589]

Forgive me for this being so long, I'm trying to cover all of the basis questions so it can be narrowed down by providing the common answers. My girlfriend had set up her fish tank about a month and a half ago. A month after (so the tank would develop algae and such) we decided to go get some fish for it. She has beach sand (purchased not dug up) and live rock from a place called Fishy Business quite a ways back. She used to have Damsel fish, but when she moved they went bye bye. So she had set up the new tank, after a month she double checked the salinity levels and it was reading the proper 1.023, so off to Petco! We ended up purchasing 2 clowns (ocellaris species), a Royal Gramma, and a false lemonpeel. About a week and a half after placing them in the Royal Gramma dies. She fished it out and flushed it so the levels didn't raise. But then about 2 days later the lemonpeel dies leaving only the 2 clowns left. She didn't notice the fins or the fish being attacked, either of them. They just floated to the top. As of right now the clown fish have small white spots over them and the tank is a little cloudy (I'll provide pictures.) We went up to Petco again, grabbed some chemical tests thinking it's the algae levels but figured nitrate/nitrite, and a ph test definitely wouldn't hurt. But everything came back fine. The ammonia level came back a little off, so we put it a few ammonia fix tablets to help drop the levels, she did a 20% water swap and the salt level always remained fine. Our only thought was that the royal was sick, causing the disease to spread through the tank. We are stumped as to what it could be because we are still fairly new to saltwater tanks so I figured posting here might provide valuable help. I go through the forums for answers to things while I was learning the basics but I just am at a loss for words. Any help would be greatly appreciated, even if the clowns die, we can prevent it from occurring again.

Sorry if the clown fish picture isn't very clear, camera wouldn't focusing I assume because of the glass.