The shrooms were grown under the blacklights 24 hours a day and the lights were hung very close to the terrariums. What happened was that the intense constant glare of the UV rich light damaged the spores and caused the albinoism. Basically said, the UV killed the shrooms because eventually they stopped fruiting.
These following links have the story. UV rich light is considered instrumental in mutation formation and it is never good.
ALBINO page one
ALBINO page two
ALBINO page three