Hey Bud
Your problem there is two fold, first your lower leaves on the plant is resting on the dirt(burrowing leaves), secondly causing a moisture build up between your soil and plant cause your garden soil is too moist and the veg at bottom is too moist. Wipe that mold off with your fingers, and cut any leaf hanging in the soil. Or low.
Once you have done this, take a peroxide to water mix of 1:2. Spray the bottom of the stocks and where the mold is, working it gently with your fingers. Then don't water for a bit and when you do cut back amount. You'll be good to go.
What that mold will do, is grow up from the soil up the stock and kill the stock, when this happens there will be nothing you can do.