Don't worry about the height of the plants. It is most important at this stage to build a full body and then the growth will come later. Early next spring cut them back hard leaving only 4-5 strong stems and when it starts growing in the spring pinch the growing tips to create even more branching. Continue doing this until mid June the then stop so it has time to flower.

Duncun msu is 100% correct / Great Advice!

Thanks duncanmsu and hydrangeasnohio, I will take your advise.