I have found that the amount of blue in the lights may cause more stretching more blue spectrums in the bloom cycle can cause some long stretching. And it may be strain specific as well. If you have your Temps in check your humidity in check and nutrition in check and light spectrum in check then it may be the type of cannabis you have. If hight is an issue try some LST and train away if you wish. I have found from my own little testing to water first light they tend to stretch less imo may have been they type of cannabis in question but I can't say for sure. I also watered before lights out and found they stretched more and it was the same type as the one watered at first light may have been difrent phenotype but it was a solid strain with little to no different sisters so to speak. Are you using hps or led