You shouldn't need to use any fertilizer for a little while still. Soils that are prefertilized, and soils you fertilize yourself, generally have plenty enough nutrients to get the plant well into veg without the need for added nutrients. I've used Alaskan fish emulsion, and still occasionally do use it, but I never have the need to use any until after the first month.

It'll be much more suitable when you move everything outdoors, and the plants will sucking up as much Nitrogen as they can get.