When should I starting to use nutrients?

I would hold off on nutrients for now, especially if the soil is already rich. I would wait until the plant at least sprouts and you see green. Even then, seedlings don't require a lot of nutrients because they are more focused on developing their roots, and it will get what it needs from the soil. I would only water gently, and then start introducing nutrients once it has at least 2-4 sets of leaves. Hope this helps. Cheers.