I was thinking that this might be a case of velvet, I had an episode of it ode and lost lost all but 1 out of 8 fish. It is very hard to cure if not caught early enough.

I am not going to even touch any of the other comments because it does not pertain to what the cause might be.

When my tank was hit with velet I did not add a fish or invert of any kind. It was about 4 months after I bought a complete system and I was still learning about SW so I was not ready to add any thing. Where it came from is still a mystery to me. It might not have come from the new fish at all.

Good luck with the rest of your fish, hope they pull through.

Gee thanks. Thats very nice of you.

Sorry for the losses, dude. I know how yer feelin'.

My guess from the sounds of it is a bactieral infection or velvet.

It can come on anything, corals, plants, anything. It can come with the water in the bag of invertebrates, on snails, pretty much anything that is not quarantine. That is why it is wise to quarantine the corals and everything when possible. 8 weeks without fish and the velvet is gone, no need to treat if the tank is fishless. That is why I always put everything in my frag tank for 8 weeks before I put it in my main aquarium. All that is needed to contaminate the tank with velvet is a single cyst that survive. Best way to id the bug would be to examin a scrape of the fish mucus with a simple microscope.