Stopping in height is not possible for a healthy plant.This plant always looking for the sun,keeps growing vertically until final point.When they start flowering,they will use more PK than N. You can still give bloom fertilizers in vegetation but plants wont use that much PK in veg. My opinion; for most indoor strains, right after first week of flowering is the week to show signs of gender.I would start giving bloom from the end of week 1 of flowering.Let some P&K drop into soil before going fully into flowering,this will help your plants find bloom nutes in soil when it starts to form buds.this might help a lot.Just dont overfeed please