strange problem with peppers, need advice

I'm having an odd problem with some peppers in my greenhouse. They are planted in plastic pots. Most of the plants look fine, but five have strange discoloration and shape. This is concerning because those five were planted into potting mix that I used last month to grow brassica greens. The greens grew well, and once they were done I pulled them out, mixed some more Epsoma garden tone fertilizer into the pot, and planted the peppers. The healthy peppers nearby are growing in a very similar potting soil mixed up from scratch.

I assumed that there was some sort of nutrient deficiency; maybe the greens had used up some micronutrient that the fertilizer didn't supply. So I sprayed the plants with Biomin micronutrient solution, which supplies Nitrogen, Magnesium, Boron, Copper, Iron, Manganese, and Zinc, and with dilute fish emulsion. No change.

I'm attaching pictures of the sad plants and the healthy ones. This problem is concerning  primarily because I have a lot more of the used potting mix, and had counted on being able to use it multiple times. If I have to mix up new potting soil for all the peppers it will be economically unfeasible.

Note the upward pointing leaves, pale color, and patchy lesions.

Any thoughts?

Did they germinate in that soil, or did you transplant as seedlings? If that's where they germinated, I propose two experiments:

1) Fill a new pot with the same soil. Place a seed on the surface. Cover with a light sprinkling of new dry soil or peat moss. (Or a peat moss replacement.)

2) Sterilize some of the same soil in the oven. After it cools, plant a pot with it as normal.

I'd plant one the same as you did before, as a control.

No, I transplanted as seedlings.

It could be a pathogen of some sort, but the greens germinated and grew nicely.

You could still try sterilizing then, but experiment 1 (with new dry soil on top) is probably irrelevant. I was taught to do that to avoid damp-off.