Can u take the rocks out of the tank? If so, you can torch them off with the handheld propane ones. Otherwise, cut them off and treat the foot with kalk paste like u would for aptasia. As with aptasia, treat only a handful per day... It will take a while. You can also bring your rocks into local stores and offer to trade them over for non 'infected' rocks
. I did this for a while and cut my population down. I also had a heat spike a few years back and noticed the mushrooms substantially died off while the encrusting algae stayed, but this would kill things like zoos as well. Low 90f for ~24hrs was what knocked a lot of mine back.