Spyder7answered grow question 5 years ago I grow autos, but the process is essentially the same:
a. Trigger flower (12/12)
b. use transition nutes (or "early flower nutes" that are still high in N but higher than veg nutes in P and K, though not full bloom ratio)
c. After the pre-flower stretch (2 weeks) begin tapering the N way down (its needed for the stretch), and the P but up the K (a pure bloom ratio.
With autos, I can't trigger the switch with lights (or I could but I don't) but I still follow the same nute cycle as the cycle is the same.