You have already added fertilizer? Nooo!
That will kill your seedlings. They aren't strong enough to take it for the first couple weeks.
Also as deft said 12/12 isn't ideal for seedlings. In nature, they are meant to sprout in springtime when days are long. Giving them the impression right from the start that it is near the end of the season is one of those stressors that could potentially give you hermaphrodites and/or a shitty m/f ratio.