I have most of my seedlings getting a nice light breeze to keep them fighting to stand straight.
95 watt CFL over tray
water daily w 1/4 nutes and 1/4 dose Olivia's rooting solution in PH'd water at 6.5-6.6 the plants love the mix.
I add the Olivia's along with the two nutes following the Fox Farm nutrient guide.
As for the Twins I Decided to leave them together and let them grow up 1 central Stick for support.
natural selection will probably kill one....
I just started showing the 2nd pointed pair of leaves on 5 of 7 seedlings.
6 more just cracked and placed in rock wool under 2 smaller domes made from 1/2 of a two liter container.
I use the bottom piece and drill a few holes on top for warm Air to rise. 3- 1" cubes fit snugly in a two liter dome.
peace,
DZ