I can't see little green dots in the dirt, but I can tell you what most likely the issue is - overwatering. Yellowing is the first sign of overwatering, and over-wet surfaces can also become home to green algae. Back off on the watering - pepper plants tend to like things more humid than wet. Most of us let the leaves wilt just a tad between waterings, as that is the best sign of when it's time to water again.
Also, be sure to get a fan onto the plants. The fan will help dry out the surface. If you let it stay too wet too long, it might also develop the damping-off fungus, which will kill the plants.