First need to get temp way down between 78-82. Thats to high for any coral. Its really hard to tell it could be a parasite is digging into it. I'll research more for you. I remember seeing it somewhere about that. Have to look it up again.
My best guess without more pics and or without seeing it. It may be splitting. This was a recent move and many soft corals will split after a stresor. This helps guarantee the survival of the species. By splitting during a stressful event it helps boost the numbers if one dies. Anemones do it all the time. Leathers are very very easy to frag and trade. Just cut em with a razor. Now if any of hte pieces look like they are melting and have actual necrosis, cut the death away with a sharp razor and then dip the coral in a Lugol's solution to prevent infection. Basically an iodine dip. About 10 drops of iodine in a half gallon of tank water. Soak the coral for about 3-5 minutes and then return to the main tank.
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