Have you been feeding the plant molasses or any other form of organic fertilizer ? If so stop because molds grow lightning fast when they are fed.
Most molds are harmless & wont affect the root mass,best way to keep mold away is to block light from reaching the soil,cut a peice of reflective material to fit over the pot & fairly tight to the stalk,this will stop mold from regrowing.
When you said somebody told you the plants were being overwatered did they instruct you how to properly care for the plant ? Between waterings the soil must ge completely dry,were talking sahara desert dry where the top of the soil will turn to powdery dust when rubbed between your fingers,the soil must be allowed to become COMPLETELY dry all the way from top to bottom,if not the plant feels stress,grows slower,is more likely to have powdery mildew,root rott is also a possibility.
Most new growers over do everything thinking they must be giving the plant something at all times & thinking more is better,with mj less is best,only water when the soil is 100% dry,the next time you think the plants need water wait another 3 days before watering.
Under watering is as easy as pie to correct but over watering can fuk the plant all up.
