Nutes especially if sprayed from a foliar( even at low doses) can show up in the so-called hairs/trychs. Usually this would be light over exposure, if it is not plant maturation, but at 3 weeks, I would agree it is a bit early to see amber hairs all over the plant. Heat, heavy amounts of potassium or chitosites, a foliar spray that is heavy in potasium or extreme air movement(wind burn) could all cause this.
Most likely though, if you are past 6 weeks in the flowering stage, it is just maturation of the plant.