Dude, wait until you transplant for all that crap, get roots first, then feed them. Not the other way around. When you dig out you hole for transplant, sprinkle some mycorrhizae in there, as well as mix it throughout the soil. Then hit everything with some humic acid, and a tablespoon of molasses per gallon. That should set everything off well enough. Seedlings are best left to their own devices IMHO.
Also, although its too late now, I use a smaller pot (8oz cup) for my seedlings, usually transplant in 10 days from seed when the roots just start to push against the cup, then they explode with all the new room, the nutes, and the mycorrs. Again, that is just me, there are a million roads to the same destination.