As long as it's not turning black or decaying it's fine. May be shedding, is the top shiny? Water change just would have pissed it off again and prolonged it opening most likely, toadstools will live through anything but are also very touchy to change and react by closing up. I usually don't bother with mine unless they stay closed up for a few weeks, then I will move them or change the flow and that normally works. But don't go moving them all over the place nonstop because they will never open.