How tall will my plants get???

I have two purple power plants growing in the ground outside. They are already 4 feet tall and I was wondering how tall they will get. I live in so-cal and its only mid june. I topped them already and I was curious how tall they may grow? Please help

well they wont flower till around the first of september so they will grow till the light cycle changes which is from summer to fall. so i see you still have a while of veggie mode so good luck and you will have a lot of bud too