What will the rosin spray answer?Several reasons this could be happening. One is a temp diff of 15 degrees or more will cause stem purpling. 2 A possible mag def. 3. Genetics. Dissolving a tablespoon of non scented epsom salt in a gallon of water and lightly spraying your leaves just before lights out will answer that question for you. Keep us posted!
Sorry, Mother Earth coco 70/30 , rocking w Athena blended nutrients, Trying to follow chart a bit a feed similar EC but got the slightest tip burn. From looks of it grow a & b doesn’t have much of any p-kI would agree with the Epsom as I would be more concerned with the Mg def I see in at least one plant then the purple stem. Maybe you should include media and nutes you use.