Please go into chat, time could be of the essence...
OK, I waited for about 15 min. you must notta got the post....
I suspect it is either a "brown jelly" infection, or your coral is managing it's zooxanthellae population. On is harmless, the other is catastrophic.
If it's zooxanthellae, then it's no biggie and it will happen from time to time, it will manifest as a brown slime stringing from the mouth or individual polyps (on corals where the mouth is actually in the center of the polyp).
If it is brown jelly it will manifest a a brown jelly like substance that consumes the flesh of the coral, very rapidly. It is an opportunistic infection of dinoflagellates (not unlike and related to the zooxanthellae in the coral
). There are coral dips that may help, Seachem makes a good one, I've heard Kent's isnt that bad either, but I like to use a FW
dip for hard corals and use the Seachems for softies. If using the coral dip, follow the directions on the bottle, if doing the FW
dip adjust temp and ph (dechlorinate) and dip the coral for 1 minute. Before the dip you should siphon off the jelly with a small diameter hose (like airline tubing), after the dip you should put the coral in an area of high water flow, this will hinder the dinos from settleing on the coral again. Watch any corals close to it carefully, it is contagious, although a healthy coral doesn't usually become infected. Repeat as needed to control the infection. This stuff is fast, if you do think it's brown jelly, at this time of night I would go ahead and FW
dip it, otherwise you may not have a coral in the am, just a skeleton.