If it's Black Gold Natural and Organic (the orange bag), the website says it's 0.05-0.0-0.0. Ingredients-Earthworm Castings, Canadian Sphagnum Peat Moss, Compost, Perlite and/or Pumice. So it has a little nitrogen in it from the earthworm castings, but that's it. It does look more like light burn than nute burn to me. Nute burn, in my experience shows up at the leaf tips first. Just keep an eye on the light height in the future and the plant should heal itself. The plant looks healthy and you can start adding Iguana Juice soon. I started adding it about 2 weeks from germination at the rate of 1 ml. per liter. I'm useing it on a feed-water-feed schedule and it seems to be going well. I increased to 2 ml. per liter the following week and 3 ml. per liter the week after. Use you own judgement though as different strains have different needs. When I start out in dixie cups, I have holes cut in the bottom. When roots start growing out the holes, it's my indication that thier ready for transplant.