I am dealing with the same problem my friend. There is only a way to slow it down. Spores are entering through another cut on this plant, maybe a trimmed branch, this causes pith rot that can only be slowed down. Feed Epsom salts. Make and use hydrogen peroxide and Isopropyl Alcohol wipes. daily on the infection site. Also DO NOT DEFOILIATE. The immune response to fight with this disease is to use its medium fan leaves first, and when the largest fan leaves start to go you know she's got to come down or your risking the advancement of this disease or bud rot. A few fan leaves a week, can be sacrificed by the plants immune response, do not overfeed water.