Is CalMag required during the flowering phase?
I am growing indoor with LEDs, Fox Farm nutrients and Miracle Grow potting soil. Height is the reason I need to force flower.
Got it. You may want to have CalMag on hand. In my experience, some strains will become deficient in calcium/magnesium if not added along with FoxFarm nutrients.
It all depends on if your Base Nutrients have enough for your plants or not. Growing in coco coir and/or with LEDs tend to require more calcium/magnesium. Most growers run CalMag as an addition to their base nutrients.
Have you watched the grow series video? Or read the section of this site labeled cal mag? I suggest checking that out.