Hard to say with info provided, but the leaf tissue is likely being damaged from the exterior, and guessing only with info provided, I'd day all the neem for unknown reasons combined with the very frequent for whatever reason foliar feeding is likely stressing the leaf tissues. The stem is something chewing it, hard to say what but the below-ground mass doesn't look right and I wonder if all the nutrients are weakening the plant below-ground and whatever is chewing it is opportunistically availing itself of all the unnamed nutrients...

Dan

Everything I am reading about Southern Blight seems to be what is going on with the plants, except I have seen no white mold and the base of the plant. The plants seem to be getting worse.

That doesn't look like southern blight to me -- in fact, that barely looks like yellowing to me.

I think your pepper plants would benefit from a bit more benign neglect. All that neem and fancy food is overkill IMO. Peppers are really tough -- they like a little more challenge in their environment. Have a beer or an iced tea and quit bothering them.

Everything I am reading about Southern Blight seems to be what is going on with the plants

The information provided shows no indicator of Southern blight that I can see.

What Mary said. There is zero reason to spray neem willy-nilly, nor any reason to waste your money on foliar feeding every 5 days. The outcomes of all that spraying and neem are visible on the pix provided.

Dan

Also like what Mary said. I am a bit of a newby in vegetable gardening, but I've had a few successful pepper plants that never received anything other than pure compost - veg scraps/daily coffee, random weeds & fruit scrap (no citrus). A few scoops of this completed compost + worm castings = 5' x 3' congo pepper tree within a year.