I think it's either that they're sensitive to something, or it's genetic. If it only happens to 1 plant out of a bunch on the same feed and schedule, I don't think it's the feed. Could also be dark because there's less leaves to spread the N out toIs it just me of does it seem like most of the three finger or less leaves that I've had or seen seem to be on the verge of too much Nitrogen? Is there a direct correlation between them