How soon after the feeding did the leaves start to brown-up? And no...it's not normal for this to happen.

Seedlings in soil shouldn't get any addition of nutrients till between the 3rd and fifth set of true leaves. (approx) Also, how long ago did you add the nutrients?

Are you in coco or soil...? If in a potting soil, next time, you might want to use the proper troubleshooting form. The one you filled-out is for hydro. The soil form is just above it in the same troubleshooting form thread.