Heavy nitrogen late in bloom keeps a plant green but does nothing for resin, and often delays ripening by a week or more. Feeding schedules that taper nitrogen while holding phosphorus and potassium are outlined at https://potentthcseeds.com with week by week targets. Most deficiency panic in the last fortnight is just normal senescence. Letting the fan leaves fade is closer to correct than fixing them.
Interesting point about nutrient timing during the flowering stage. Overall plant health and physical development are important factors to consider, just as understanding body shape can help when looking at individual physical characteristics. The distinction between normal senescence and an actual deficiency is especially useful.