I'll expand on pcduck's advice that is right on target. You've let your plants out-grow your grow area limitations. MJ plants almost always DOUBLE in height during flowering and can TRIPLE their height sometimes.
Here's a plan to resolve your problem that will cause you a LOT of heartache unless you follow it.
As soon as you've placed your plants into your flowering area, you need to *start* pulling them over. You can use any sort of weight, and tie some string to it. Then, GENTLY pull the top of a branch over until you feel a TINY BIT of resistance. IF YOU PULL TOO HARD you'll lose your branch because it'll snap off.
ONCE per/day, pull each branch over a little more. Your goal is to bend the branches back, ALMOST TO THE FLOOR AGAIN. This can be done in daily, SMALL INCREMENTS. Each day for about two weeks, you'll have to pull each branch over a little more until they are looping back towards the ground. As you turn them, you'll notice that they will adjust by again turning their tops toward the light. This is good.
Once you have them back to a MAXIMUM height that allows them to more than double without hitting your lights, take a break from turning them and watch them closely. You'll see that the uppermost part of each branch is now growing faster than any other part of the "old" tops.
This is because plants create a hormone for "top growth" that is directed ONLY to the tallest branch tips and is strongest on the tallest of all of them. That hormone makes the tallest branches grow faster than any of the others.
You can keep this hormone from selecting a single branch by keeping all of the tallest branches at the same height. This will cause the plant to evenly distribute that hormone among all of the tops, not just the one that is tallest.
BE WARNED THAT if you get in a hurry and disregard my warning to be very, very gentle while pulling these branches over, you MAY BREAK ONE or more and I promise you from experience that it will piss you off like you won't believe.
Good luck. You've now progressed a little further on your learning curve. You'll flower your next crop before it's too tall.