I suppose it is possible that your lights might have started it but that would be unusual assuming normal lights. But any damage that happens inside is only quickly magnified once the plants are exposed to full sun. And "shade for a couple of days" isn't fully hardening them off.

At any rate, if you will move them out of the direct sun into a shady sheltered environment outside and protect them for winds (which can also damage leaves) for several more days they should recover and start putting out new growth. The badly damaged leaves will continue die and eventually fall off. I'd cut them off now to reduce stress on the plant.

Coloring of the healthy leaves in the photo is anemic but that may be the camera effect. So what and how much have they been fed? They should be much darker green at that size. You are also going to want to see if they are rootbound in those small pots.

Dave