They kind of veg and flower at the same time , around week 5/6 they stop growing upwards , that's the stretch done , then autos stop using the nitrogen so much and go flower mode ,p.k
you can also go a little too much then it gets locked in when they stop using (N), it can be worse than under feeding them ,they lock up , then you think it needs fed and you add more nutes to the problem ,
your on the better side your girls are just hungry
go light with (N) but not too light and you will be grand your next run start switch at week 4/5 slowly