Sancho,
I'm currently having this exact some problem with my Sheffeala or whatever it is, I don't know what to do. New ones pop up every day and they are gone by the morning but there are new ones. I started picking them out but they keep growing. I'm thinking about just trashing mine to not only because of the mushrooms but the actual cage reeks from something and i can't figure it out... I'm starting to think it's the soil I replanted it with. Now that it's just about spring time I'll be able to find a nice 4 foot ficus around here.
Just my thoughts