I couldn't give any sage advice, I'm still a newbie. I'm growing in dirt, (off brand but comparable to promix ultimate organic) and have issues on week 3 when they get done stretching and start packing. I'm on my 3rd run and stuff is getting better, much of my problems were underwatering. Even fixing that I still got issues at week 3, though not as bad. I decided to start liquid kelp (growmore) and can see a really big difference so far. My other nutrients is a very sparing dose (150 ppml of miracle grow 18-6-12 (ya i know, but it's on hand and it does work). Don't know if this helps but maybe try the kelp. My plant are way happier, I'm trying a perpetual and can see when this made the rotation. I have started adding calmag also just because of the discussion here. I'll know more in a couple of weeks. I run ro water so it not like it's gonna hurt. It stands to reason that if cobs require more calmag then maybe there is another micronutrient that is also needed in greater quantities.