That's what I call, Canna - balism.
N deficiency, as someone already mentioned, grow weed easy.com has some brilliant information for growers of all experience. You should check it out, it'll give you an idea of what you're looking at, or even just to read up in your spare time.
I can't exactly see your pot, but my spidy senses' are telling me, you need to transplant.
Other than that, they're looking beautiful.
Keep it up.