they start to flower before actual 12/12 outdoor.
12/12 indoor light schedule is just cause that works on pretty much all strains. a lot of people tweek their indoor timers, but we all just say 12/12 as a rule to make things easier. it's not set in stone
mine are starting to (slowly) transition to flower now too, and i'm more northern than you.
i assume the question is; should i stop feeding veg nutes, not should i stop feeding. period.
obviously you need to keep feeding. in bloom more-so than veg.
you're likely seeing some pre-flower stretch like nc mentioned.
i always stick with my veg feed untill there's actual buds.. a lot of time they like to stay looking mature for a bit first, shooting pistils, but just faking you out.
i've found in past years they'd yellow/start fading on me too early if i went to bloom nutes to early.
lookin good though, nice job.
good luck down the homestretch