I live in a very humid climate. Mold is of a type of fungus, mildew is also a type of fungus and is sometimes used interchangeably. I know very little about either, and I was unable to find much help in my reference books or on the internet. Because there are so many different types of fungi it is difficult to know how to fight an outbreak. Mold propagates by spreading a millions of spores, which travel through the air.
Mold spores are everywhere, and can grow on almost any organic material.
If it is active and it is in single plant, consider withdrawing it from the collection, and carefully remove and replace the top inch of soil from the pot. Some varieties of mold are toxic to humans, so please use great care. Wearing rubber gloves and a dust mask are not unreasonable precautions. There are fungicides on the market that will kill the mold, check with your local nursery or garden center for an appropriate one, and use only according to directions. I wish that I could be of more help, but I think you can easily defeat the mold.