my version might be a bit expensive and time consuming, but it is surefire. i used this on green star polyps. i scratched off as much as possible.(in your case i guess cut off as much of the shrooms as possible.) and then cover the areas in reef cement(mine is the stuff thats white with a green layer on the outside.) depending on the amount of space, you may have to use a lot. and then wait. and wait. you can either cover it with other corals or if you wait long enough (+6 months) you can flake the stuff back off.