I understand that hardening off means that the plants are gradually introduced to the sun and the elements, and that's why I've been trying to do. But, after my plants have been exposed to the sun for a short period, do I bring them inside and put them in full darkness, use my grow lights, or place them next to a window?

Also, I have many hot peppers (not seedlings), as well as cuke, tomato, basil, and eggplant seedlings that I've been trying to harden off. The seedlings came from a nursery where they were outdoors under an opaque sun shade. I started by putting everything outside for 30 mins in bright shade/direct sun, and I've been increasing the time interval outside. However, I can't seem to get anything to look OK beyond 2 hours. They wilt, they look sunscalded, and I'm not sure what to do. Any help is appreciated. Thanks!