Mold is a sign that your soil is too wet and your pots are in an area that isn’t receiving enough light and airflow. Avoid scheduled watering and only water your soil if it is no longer moist.
Here are some tips for getting rid of mold:
Remove plant markers and clean using a diluted solution of 1 tbsp. apple cider vinegar mixed with 32 oz. of water. Allow to dry completely before placing back into soil. When placing markers back into pots, do not stick them all the way to the bottom but, instead, push them down far enough so that they are supported (about 1 1/2" deep).
Sprinkle cinnamon lightly over top soil. Cinnamon acts as a natural fungicide and will quickly get rid of any mold that is present.
You can also use the diluted vinegar/water solution as a spot treatment for mold, but avoid treating your plants in direct sunshine as this can lead to leaf spotting.
Again, to prevent mold growth do not overwater your soil. Your soil should be moist and never flooded with water. Check the moisture level by sticking your finger into the soil about 2 inches deep.