Why is my new growth yellow?

I have to say it is light stress or burn says 12 inches from light. Too close. Yellowing in upper canopy is light stress at that distance for sure. I doubt your root bound, and cal mag does not match symptoms well. Light burn would be my answer from available data.

Gotta disagree with MrWeeds here, looks root-bound to me, meaning the pot is too small for the plant , so you're getting a bunch of different symptoms and they will get worse. Transplant to a bigger pot and it should bounce back in 10 days or less. Hope this helps ! 🚀

This is calcium deficiency a calcium deficiency results in yellowing in new or younger leaves. This is because calcium is an immobile element; as a result, the calcium ion cannot move freely between old and new leaves. Thus, leaves will grow in inherently yellow.,