She's looking good so far. When to add nutes depends a lot on what's already in your soil. If it has any time release fertilizer already mixed in, you may not need to add anything for quite a while.
I'd watch for any signs of yellowing on your lower leaves. When you see that, you probably need to start feeding. Start slow with young plants, maybe 1/4 of whatever the bottle says.
I burned the shit out of my first crop when they were young, and it took a while to recover. My next crop I did the opposite, no nutes for about 5 weeks. I was so busy worrying about my flowering plants that I just didn't realize my vegging plants had stopped growing and the leaves were yellowing.
I gave them a little 5-1-1 fish emulsion and they perked right back up.