well, you don't want to transplant at "night" and risk light stress / hermies, so I'd say definitely during lights on. towards the end of the cycle is a good idea.
I usually do them one at a time so they're out of the light for as little time as possible.
I also don't give them any nutes for a watering or two, before or after transplant. I wouldn't recommend adding nutes to your new soil, the new soil should already have fresh nutrients in it that won't be depleted yet. you don't want to risk burning the roots or stressing it too much