What’s wrong with my pepper?

What’s wrong with my pepper?

I've never had very good luck growing peppers, so I was excited when this year's pepper plant seemed ready to produce a healthy crop. Then, as the peppers started to mature, almost all of them began to show brown spots near the bottom that grew and became sunken over time. This photo shows both an advanced case and one that's in the earlier stages. As you can see the rest of the plant appears healthy: I've never encountered this problem before. Does anyone know what could be causing this? What can I do to resolve the problem? If it helps, I'm growing the plant in a container on my deck where it gets very full sun. I live in Philadelphia--zone 6. Thanks!
My Happy Home

My Happy Home

buds and seeds

buds and seeds

Sunflower stems ?

Sunflower stems ?

Room!

Room!

What my room looks like when you enter

What my room looks like when you enter

Plant ID!

Plant ID!