Too much N --> long and slim (weak) vegetative plants or too much nutrients in general can also lead to reverse osmosis which causes the yellow leave.
Not enough N --> Plant will grow slow, leaves might turn yellow as well because of 'underfeeding'.
It's mainly Kalium that makes the leaves grow thick/dark green + the amount and spectrum of light(mainly the red/farred ratio).
I don't believe in tea grown with barely any nutrients nor in tea with too much. A plant just needs healthy fertiliziation just like a human needs quality food. Cows taste the best as well when they had some nice grass and quality corn to eat, not when they are near starvation or overly fat.