Your coffee maker should be made a part of your regular kitchen cleaning routine. Mold can grow in the variety of places in and across the house. No matter how good your memory may be, one particular stored foods don't ring familiar. All your mother's prized antique furniture, even the Louis XVI armchair, is stewing inside a half-foot of cloudy water.
Dampen any moldy materials and surfaces. It's probably dust over the plates it has.