I dont have any experience with HID grow light. MAYBE (?!) your plants are just curling because of the intensity of light.
Are those symptoms across the board or variety specific ? How about their position relative to the light source ?

Another issue is growing in ORGANIC potting mix with worm casting..etc. Again, I have no experience with it. Most people use regular potting mix (soil less) when repoting into 4 -5" or bigger pots. Most commercial potting mixes have whatever the seedlings would need (nutrients trace elements like Ca).
So in short, Your whole system is not quite conventional.
Wait for more comments.

Seysonn

One more thing:
In my quick/brief search in the internet, I noticed few people had the same problem and they were using VERMICOMPOST ??

i got the same issue, even when my plant is only sitting indoors. Yes, excess nitrogen is something what even i thought and i started adding some egg shell powder etc to my composting mixture (as a compromise)..I have no choice of obtaining any sand-mixture and i truely dont know the composition or details of the composting they sell (no details written on the packet).

If it was me at this point, I would take the plants out, shake off the loose soil and repot in potting soil and stop fertilizing.

Seysonn

A close look at the bottom left plant in the bottom pic I see some specs. As well as leaves that look a little bit more shiny than the rest. That makes me think aphids are possible. Hold the plants up and look under the leaves. Also hold them up to a light. If they are there you will see them. If leaves look like they have shiny oil on them run your finger on it. Touch it to your tongue if it taste sweet, then rest assured you have aphids.

I don't think I would do something that drastic. The deformation is not killing any leaves, and otherwise the plant seems healthy. I am not fertilizing. Especially since Every person that has commented gave a different idea of the cause, there is a duplicate post in another forum. I was hoping for a larger consensus.

Thank you for the ideas. I think my best guess at this point is Oedema. Possibly grow light heat as well... both of which can be managed with the fan I added until they get larger and grow out of it.

Thank you very much for the comments and ideas.

No aphids. I've looked over the plants with a magnifying loop. The specs are pepper plant Oedema.

I have had more than a few get crinkled leaves this year. Most have seemed to out grow it. Two of my best producers last year had leaf curl like no tomorrow. Yet they just kept on putting out pods. As long as the leaves are not dying off I would not worry about it.

The plants look otherwise quite healthy.