not sure without more info, but toadstools in general shed a top layer of skin anywhere from weekly to monthly and won't have polyps extending for the 2-3 days before shedding.. normal process and they look just as good afterwards..
i noticed when i had toadstools with stonies that there seemed to be a lot more shedding going on (weekly instead of monthly) which i was thinking of attributing to chemical warfare, but not sure..
if toadstool beings to look like its melting that is a bad sign.. if bits of it (not clear top skin layer, but small chunks) start coming off if you turkey baste, or just looks like its disintigrating really bad/fast then try to frag and get rid of the rest as it makes a mess of your tank..