My leather coral has this wierd shiny coating on him and he's not opening up. He's not shedding his skin either. At first I thought I might of been slime from a snail?
This happens to my leather from time to time. If it doesn't clear up in a couple days you can gently try to blow the mucus off with a syringe or turky baster. If the coral still doesn't open up, or re-coats itself after you've removed the mucus, you may want to try moving it to a new spot in the tank. just to ensure that nothing is bothering it in its current location.