Welcome! Sometimes, chameleons take a while to grow. They are, but just slowly. Do you gutload your feeders? How much do you feed a day? What wattage bulbs do you use? And also, do you use calcium of your feeders? All of these can effect a chamleon's growth.
I only have 2 crape myrtle trees ( which have some disease) and a small lime tree with really skinny branches. My closest neighbor's tree has to thick of branches any pretty much all of my friends don't have a good tree. Is there anywhere I can buy them from, knowing the length?