thats the same problem i have had with my mushrooms. i have had a 40 gallon tank setup for about a year now and i have purple mushrooms, red mushrooms, purple with blue outlining and purple with blue speckles that are doing amazing and have been dropping babies likes crazy. i went from one of each to over 15-20 in a few months. my green one however has from some reason not done a thing. it was doing great for the first 3 weeks or so, one of the best looking ones and was always open and happy then one day he decided to shrivel up more and more and more until he finally detached and is now attached under a rock out of the light and is still doing terrible. i think he is about ready to just give up.