Slowing the grow by purpose

Maybe a little stupid question but anyway, do anybody know any ways to slow the grow?
Half of my girls are 2 weeks older then others, so i would like to slow the big ones a little bit so i could put them to flower in the same time at aprox same height...

Topping them is the easiest way to keep them the same height.

Stick em in the freezer




What he said^^^^

Top and tie her down