Why have my chilli seedlings stopped growing?

Question

6 days ago, I repotted some chilli seedlings after they started showing their 3rd pair of leaves. They were the biggest seedlings at the time. Since then they seemed to have stopped growing. These are the ones in the green planters in the picture.

I left some of the slightly smaller seedlings in their original planter. These are the 4 seedlings in the black planter in the bottom left of the picture. You can see that they are doing much better than the ones in the green planters.

I found a question about stunted seedlings, but mine don't look malnourished:

Why have my lemon seedlings stopped growing and turned yellow?

What can I do to get the green planter seedlings growing again?

Update

It took a while, but my chilli seedlings have started growing again. I have been lightly fertilising as suggested, I can't say that it definitely helped, but it certainly didn't hurt the seedlings.

Answer 1

I'd say the stress of replanting is causing this non-growth. Small damages to roots and new type of soil. The seedlings need to recover.

I'd be patient.

Answer 2

Without knowing where you are, and basing my answer on where I am (eastern Long Island, NY), I'd guess they got cold. Cold sensitivities vary, but growth will slow dramatically if they've been exposed to temps in the low 40's for a night or two.

Answer 3

Transplanting peppers can stunt them for a while (potentially much longer than six days). However, if you give them some extra potassium sulfate and put them in very bright fluorescent light (very close to it), they should overcome that pretty fast. You may also need to add calcium (such as from rock dust or gypsum) if you use very much potassium. Bright light alone should help, though. Since it's already been six days, you don't need to worry about giving them too much light due to the transplant.

In my experience, potassium helps plants to overcome or avoid transplant shock better. In my experience, extra light (after a couple days without bright light, to avoid wilting) also helps considerably.