4 plants at 2 and a half weeks. a few questions?

Hi, I have 4 pants going that are 2 weeks and 3 days so far. Ive read that around this time I need to start to give the plants nutrition and fertilizer because the soil runs on. What mix of fertilizer do i use? and how much do i put in each time i water the plants?

I'm sure someone will correct me if I'm wrong, but I kinda think that's a little early to start nutrients.

Even in the mildest form, it seemed any nutrients I used before 3-4 weeks would burn them. Just my opinion, though.:)