I have the same thing happening; hope we get answers.

I would remove those leaves as soon as you see the yellowing and put them in the trash, not the compost. New England has had an unbelievably cold and wet spring up until this week, perfect for fungal diseases which often splash up as spores from soil onto lower leaves during rain. I think the Great Lakes states have been fairly wet as well. IME most peppers grow best in hot weather, so this summer until recently hasn’t been conducive to good growth on pepper plants.

Yes. Spray with copper aggressively. no need to remove the plant, only leaves. Did you get the seedlings from the nursery? That's the source.

I plant 50 pepper plants all varieties . Since i acquired compost (leaves & dirt ground) from the town dump, I have what appers to be bacterail leaf spot (xanthomonas spp.) I purchase my plants from Great Swamp Nursery. It was suggested to spray copper aggressively . How , what type, & when is best. How can the problem be avoided? I live in central Jersey. Any & all help would be greatly appreciated. I called Rutgers extension service to no avail. ty, Joe