Moldy Peppers Growing in Containers

Trying adding vermiculite next time, also some pebbles or shells or something that will help the soil drain as the water flows through it, the vermiculite will capture enough of the water to maintain moisture but the rest will drain off.

Mold is always an indication of too much moisture. Your soil may be wrong or kept too wet. Your humidity may be incorrect. Peppers love sun and heat and little wind. Have you moved your plants from one area to another? Are you fertilizing? It is much harder to grow peppers from seed than an already started plant you buy. Also never bother the root system of a pepper!