Just catching up on your tank progress. Congrats on the purchase and success so far.
As far as the leather is concerned, sometimes they will not open and shed a layer of 'skin' as they grow. Also, if your toadstool is anything like mine, it will drop buds, or chunks off the main coral, which grow in to new toadstools. When it starts, sometimes a tiny hole will develop and spread until a chunk falls off. I don't think I've paid for anything at my lfs the last couple of years, but used the credit I get for my toadstool frags.
Thanks...it sounds like the starting of a bud or chunk falling off. If or when it does...do I just place it on another rock to start growing on its own?