Transplanting during flowering can be tricky and risky. Assuming that you are using plastic pots like most people instead of clay pots like a few people use and if you have enough height to work with you can cut the bottom out of the pots your plants are now in and then set them into larger pots, sinking/setting them in roughly 2 inches deep into the soil in the lower pots and the roots will then grow down into the soil in the larger pots below.
 
If you go that route and after cutting the bottoms off your pots you find that you have a root-bound condition, which you are very likely to find, you can score/cut the bottom of the root-ball slightly and then new roots will shoot out and down faster and easier than if they remain as they were tightly circling the pots and being tightly intertwined.