Oh OP, in the future you might want to supp with a bit of silica and some calmag maybe.
Silica helps strengthen stems and plant cells, calmag does the same to some degree but I think it would help green up those red stems also. Lack of calcium can contribute to woody, brittle stems. If u start seeing brown spots along with the red DEF give it some calmag.
**Calmag btw, is calcium and magnesium not just one thing...