What type of lighting do you have? How long have you had the shrooms; they can have trouble under pc lighting, too much build up of, I believe, oxygen in their tissues causes a caustic reaction due to the uv from the pc lighting
I had trouble with shrooms in my first tank, had only 10,000k pc lighting and did not use filtered water, they eventually shriveled away to nothing
You could try moving them to a shadier area for some time, but again all depends on your setup???