You might be overfeeding them, as you said they are in an organic soil, which usually translates into something with a considerable amount of nutes, organic most likely, in it. When you add other fertilizers and stuff, it can react in the soil and lock out the nutrients you are trying to provide. They DO look like they have a touch of light burn, but roughly 2 ft away for a smaller bulb shouldn't fry them IMO. When plants are very small and don't have great root systems yet, adding nutes isn't always a good idea although most newer growers don't see it that way. Anyhow, that is my opinion, since most problems are nutrient related.