When my plants are growing too fast in veg I switch to seedling fertilizer and I get stingy... I also find restricting the root system slightly works. (When you do relieve the root-bound plants you just have to unbind the roots a little.) I've also had good luck with LST and supercropping when I've needed to significantly affect the plant height for flower. (In veg, if the plants are at or near the height of the light in flower, I think you would have to use LST or supercropping.) I've never tried lowering the temperature but I like the suggestion... probably the least stressful on the plant! Best of luck!