You may have a bug or something attacking your leaves.
I suggest boiling a few unscented pure cigars and lightly spray the leaves for bugs, add chili powder if want.
If it is mold, it's not bad, (but carefully examine what it could be). For mold, it's best to use cloth pots for better drainage. And add a tablespoon of peroxide to a gallon of water for your soil. It slows/kill mold growth and adds oxygen to your roots. Do only once a month if needed