If it's brown jelly, be worried. If it's nothing more than mucus secretion, and the coral tissue under the mucus looks healthy, it's just fine.
Okay. Worst scenario, brown jelly. If the mucus started somewhere on the piece and spread, it's probably brown jelly. Take it out of the tank and put it in a QT. Take a brush and gently remove the "jelly" (which is dead tissue.) Be very careful with the stuff you remove, it's a contagion. Since you're dealing with Favia, a brief freshwater dip would be a reasonable course of action to try to kill off whatever pathogen is eating the coral. Lugol's dip can be tried next if the freshwater dip doesn't seem to help that much.
If the mucus is clear and the tissue underneath looks okay, you're all set. I'm inclined to think that is the case considering you wondered if it was normal. Brown jelly doesn't at ALL look normal! Corals sometimes hypersecrete after being handled or after the adding food or chemicals to the aquarium. Also, many corals produce mucus nets that are part of excretory and/or feeding behaviors.
Let me know how your little guy is doing.
<img src="graemlins//evilwhorn.gif" border="0" alt="[Evil Horn]" /> --Oph
