I have a once very vigorous ornamental pepper (Capsicum annuum) that's suffering from a disease I can't identify. It starts with chlorosis that clusters around the central vein, and is slightly interveinal. The underside of the leaf has dark discolorations adjacent to the main vein, and clustered at the bottom of the leaf. Eventually the leaves start to get crispy around the edges, but do not wilt. They loosen from the stem and fall with the petiole intact. It seems to affect older leaves first, but it's also a little random. The plant is still aggressively flowering and fruiting, though I've been removing flowers when I can to conserve energy for the foliage. This has been going on for a couple months, but the plant will die if it continues. We do use the peppers for food, despite it being an "ornamental" variety. This plant is several years old, and has been rootpruned and hard pruned on the top multiple times.

Despite a thorough search, I've found no unusual insects, other than the occasional aphid. No spidermites, no whiteflies, no beetles, or any of their characteristic symptoms. None of the leaf spot diseases match, and none of the viruses I've looked at match either. Halp! Please.

Other peppers nearby seem fine (both sweet and chili). I don't have any other Capsicum annuum, so I can't say it's isolated to this species.

Thank you!