I had debated throwing these out and starting over, but decided to give them a chance. They were growing nicely but got some whitefly, so I sprayed them with Neem oil. The Neem burned the leaves and tip shoots. They stopped growing.
I usually cut the tip shoot anyway to make them grow low branches. So I cut those out, and am just giving normal seedling care. I usually give a very dilute solution of Miracle Gro but wondered if that wasn't helping, so bought some Schultz liquid. It easier to give as a dilute solution because it's liquid drops in a dropper bottle.
Looking very very closely, I think these are looking like they might be about to grow new shoots at the leaf axils. It might be my imagination, but I think these seedlings look a bit more robust now, too. So I'll just keep taking care of them and see how they do.
The other thing that is encouraging is they have healthy looking roots emerging through the bottom holes. They shouldn't do that if there is a problem with the potting soil. I don't recall if I used an older bacth of soil for these. But I think they are OK.
I have other pepper plants to up-pot soon. These are the pioneers which will tell me if conditions are right.