Hi,
That depends on weather your using a light mix or heavy mix. Some mediums can last 4 weeks without any nutrients, some are 6 (Like mine). For now, let her grow out and get use to her environment, less is always more so don't over do it. When she start getting more sets of leaves.. maybe 4 or so then you can add the nutrients as your plant can use it efficiently instead of it going to waste. With all the experience I've gained over my time, I don't use any nutrients for the first 3 and half weeks depending on how long I veg for. When you do start feeding nutrients, make sure you start at quarter strength of the recommended dose. Hope this helps