To treat an afflicted specimen, as much of the digested tissue (jelly) should be siphoned or brushed off the unhealthy coral as possible. Ideally, this should occur outside of the main tank. The mix of dead tissue and microorganisms shold be considered a contagious agent, as the jelly can initiate infections in nearby corals. Once cleansed of the excess slough, the coral can be given a freshwater dip for several minutes to kill many of the microorganims present (not sure if leather corals can tolerate a freshwater dip, can someone else help with this?). An antibiotic paste on the infected areas or a Lugol's dip may also be advised as alternative or additional treatments. It is best to use the least stressful methods first and see if the result is satisfactory. Excessive treatment or stress may cause a coral to become susceptible to other infection, or may result in bleaching or the loss of the entire coral. If it appears that none of the above methods are halting the progress of the infection, the coral should be cut, snipped, or cleaved slightly ahead of the progressing jelly and the healthy piece or pieces places in a quarantine tank. In some cases, the coral will be able to heal in such an environment. I hope this helps.