The color loss and receding tissue aren't what concern me. What concerns me are the mouths in the photo. They look as though they've lost their digestive system (commonly seen with trachyphyllias and acanthophyllias.) If this is the case, there is nothing left to be done unless you can find a mouth that still is intact. If so, cutting it with a bandsaw may save that bit. After the cut, you'll need to superglue down any loose tissue to prevent the flow from ripping it apart. I'd also dip it in a coral dip to help lessen any infection.
Various things can cause a mouth to disintegrate (infection, injury, etc.), and the coral typically appears healthy (extending tentacles, inflating, etc.) for 1-2 weeks before the coral entirely dies. Sorry.