zoo frag dieing, does it spread?

[lfish]

I have several differnt rocks with zoos and corals, and I noticed one of them with a brownish foam on it and the poylps were closed. I cleaned it off and dipped it in freshwater. Looked like just one of the polyps opened the next day and the rest were looking more and more like they were disapearing. Today I dipped it in lugol's. Not sure if I am doing the right thing or not by dipping it. Does anyone know what this is and if it will spread to my other corals? I am wondering if I should remove the rock from the tank? Or os there any hop eof it making it? thanks

[Doug1]

Between the FW dip and the lugols, I don't think theres a lot else to be done at this point. Check all params and maybe do a water change or two over the next week.
Monitor close and if it's still heading south pull it or quarantine

[Jackclown]

I am curious too, if one coral is ailing will that spread to others for certain