This is my toadstool, on Dec 2nd, about a month after I bought it.
When the head had just about doubled in size, the stalk started to change. It
became clear, and I could see the one stalk, inside the membrane, starting to form off a 2nd stalk. The back is smooth & even.
While the stalk was separating, the head also went through a series of splits. It
would close up for several days while it did this. You can see in this pic where the
split happened:
The top, just coming out after closing on me for the last 3 days (had a high temp
spike in tank)
Finally had to move it, when it got too big. This is when it is open:
