Probably something wrong with the mix, which is why the mold took hold. Mold and moss capitalize on nutrients in the mix, and are good indicators of mineralization. Pygmy species are sensitive to transplant, esp. if not healthy, otherwise I would advise you transplant. As it is, the best advice is to let the pot dry out at the surface. To water, put the pot in a few inches of water for 3 or 4 mins. The aim being to provide moisture to the roots while keeping the surface nearly dry. Increase air circulation by using a small fan. You might also get by with dumping the entire root ball into your palm. At this stage your palm will be cupped over the rosettes. Carefully reverse the root ball and remove several cm of the top mix, reinsert the root ball into the pot and add appropriate top dressing high in sand content, about 70/30. This will likely fix the problem, at least short term.