When is the right time to start adding fertilizer

I am attempting my first grow and looking for advice as to when i should start adding fertilizer. Im growing two plants each of pineapple express and critical kush from seeds. they just sprouted only about 2 inches high each. i know i should wait but when will i know its the right time?

About a month or so in after sprouting.

I too am just starting out and from what i understand it depends on your growing medium. If your in soil your fine for a few weeks without nutrients. However if your growing in something like coco or peat moss you will need nutrients right away but at a very low dose.

im planning on using soil. what i was wondering is what signals you to start using fertilizer is there a difference in growth or something like that to signal the need for nutrients?