Yeah I don't think it's light burn at least not straight up. I agree with Rurumo that it looks like a watering habit or moisture issue. If the rootball is too moist that can cause similar problems to over watering, clawing, discoloration, slow growth, ect. Lifting it up off the ground a little will help like suggested.
Also be careful with the nitrogen, it can make the clawing worse.
All that aside it does look good, keep at it!