rich_manure, the spots remind me of a description - water soaked - indicating a fungus but at the link below, they suggest low light and high moisture. Although the site is about indoor plants, it is the conditions that really matter.
LINK

Did this appear after you used oil on your pepper plants for the chewing insects? It really looks like phytotoxicity to me. Peppers can really get their foliage messed up with oil sprays. It's sometimes necessary, depending on the type of insect, but the leaves do look like this and they do fall. If it is from oil damage, they plant will outgrow it.

Not certain if it was after spraying or not, but I did purchase more plants and planted them is various sections of my garden in areas where I never grew vegetables before and they too are starting to get the same problem. All other plants are fine except my Zinias which have very similar symptoms. I really want some fresh peppers but not looking likely.