its your feeding regime thats slowing you down mate, you have had your girls on veg feed for quite a while so they havent been encouraged to go into flower because of the extra nitrogen you have been giving them, dont get me wrong if i was doing a scrog this is exactly the method i would have used so i could fill the screens, now you have flipped them to bloom nutrients you shouldnt have to wait to long before they start flowering for you
extra veg time = bigger yields , ive got the same thing happening in my grow as well because im so used to using a 2 part nutrient 1 for veg and 1 for bloom its easier to switch from 1 to the other but with the 3 part its more of a gradual move over so its all about you the grower getting your timings right and planning out the length of grow and having the correct feeding schedule to do it
with hydro your in control of the plants so you get to manipulate them to do certain things especially when it comes to their feed
hope this helps