There are four different reasons your pepper plants may have black or brown spots. It's typically the result of sunscald, blossom end rot, anthracnose, or bacterial leaf spot.

Neem oil and baking soda mixtures are popular choices for treating fungal issues. Pick off the infected leaves and spray them well, it could take 1-3 weeks to get rid of the bacteria. They need more airflow to prevent it spreading. Good luck, Sallybeth