Hey Growmie,
With it only being the one leaf I would worry about it too much, now if it moves on to more leaves then your going to be looking for a deficiency, but for now, I think you're safe. Feel free to shoot me a holler if you ever need any help, I'd be honored to assist you. Hopefully, this was helpful, and remember ... "Happy Growing" and "Free your mind one puff at a time".