napa is bang on, due to the autos only having a short veg cycle they normally get all the nitrogen they need from the soil, depending on what you are using. the bloom nutes also contains small percentage of nitrogen aswell(bio bloom does). if you are using small pots though then you may need to use some bio grow or similar veg nute. they are quick growers and relatively hungry.
take his advice about the micro nutrients aswell, something like bioheaven or alg-a-mic.