Try drying out your humidor and cleaning it thoroughly, you may even have to replace it to get rid of the mould. All humidors are not born equal, a cheap one can work really well and the next day it is not so good. Mould is usually caused by excessive humidity. THe area where you live is also a factor. AZ is quite dry whereas SC is very humid. That can affect your humidor.
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It may be too much moisture that is causing the mold

A little air once in a while is a good thing to keep tobacco fresh, and not over humidified.

A humidity gauge (specific name?) is cheap and really helpful to know that you are staying at about 70%.

Many humidors are wood but this is due more to traditional and looks rather than being practical and efficient. A glass container like a ball jar or mason jar of the appropriate size works better in keeping your stogies fresh.

Store in a cool, dry place.

And, although rare, some cigars can be ‘mold prone’ and then transfer the mold to the humidor

You can remove the mold with a lightly soaked bleach laden rag. (wear rubber gloves). Bleach is the only stuff that will kill the mold as it is a disinfectant. Then follow up with a soap and water rag. Then just a lightly soaked rag with water only to rinse. Let air dry for several days.