When its the right time to start using fertilizer?

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

Depends. On what? pot size and soil type. Are you using quality soil? light mix or pre fertilized soil? Whatever you are using, you should wait until the plant has 4 pair of serrated leaves fully open. If you are using a low fertilized soil, you start at this point; if your soil has more nutrients, you wait more weeks.

Its probably a little early for nutrients, I would wait till week 3-4 and even then at 1/4 strength. Also it really depends on your soil makeup (Did it have nutes in it to being with?) What soil did you use? I see grass and stuff sprouting in there.