The “shroomery” have a “contamination forum” (how’s that for a name for a message board!) which shows this (from your description) to be “cobweb mould”.
here’s another safety warning
TBH I’d get rid of these and obtain a fresh batch – after all, you would not normally eat food that had gone mouldy!
Shrooms are much easier to get (even out of seasons) than they ever were before, but the emergency ward of the local hospital is not a nice place to be in over the holiday season!