So much is unanswered. How many hours a day are your lights running? What is the temperature of the soil? Describe your seedling mix. Do you have fan air circulation? Al

Yes I do have a fan for ventalation. The seedling mix is giant bell seeds in 4 in pots and some in smaller peat pots. The curl is from plants approx 4-5 in tall with about 6 true leaves in the 4 inch plastic pots.

The cycle is 16 on and 8 off.

The soil is "M-G" seeding soil so its probably not a nutrient problem.

I do not know what you are growing and what your intentions are. Your seed starting mix is just that, your seeds are started, are you planning to pot up or is this something you are planning to plant directly in your garden? Most seed starting mixes are mostly peat and are not fast enough draining to grow a plant on for long. Your light should be OK with 3 to 4 thousand foot candles at soil level. As I read your post over, it looks like you are growing bell peppers, and if so I would transplant into a good draining potting mix and after a week or two would begin a regular fertilizing routine. I would like my soil temperature to be from 70 to 80 degrees. Al