Peppers/Chillis-however you call them, are hot house plants and members of the nightshade. They thrive under the same conditions as tomatoes - hot, full sun with temps between 50°F & 85°F. They need rich dark compost, lots of space, staking if they get too heavy with fruit.

Looking at your plants, they look recoverable. Those pots look way too small. These are very hungry plants and would use up the food/water in those tiny pots very fast. Plant them into the ground in a prepared bed with lots of organic matter and amendments. Let the roots go down deep and explore maybe give them a trellis to climb for good air circulation. You will be richly rewarded in turn.

Some signs of magnesium deficiency, and it looks like it has chili thrips, too. Magnesium deficiency is an easy fix with epsom salts, K-Mag, or azomite--or any fertilizer with magnesium in the analysis.
Chili thrips are more difficult. Earthworm castings will help the plants resist them. Green lacewings, predatory mites, and pirate bugs eat them.

Thank you very much for your help. I’ve put them where it’s sunnier and I’m going to put them in bigger pots - I don’t have enough room to put them in the border. I’ll also put them in better compost - I got some delivered today