Grow Mediums Outdoor Coco deficiency

[Ausican]

I've had a great run so far but I've noticed some spotting on the lower leaves. I think it's a magnesium deficiency even though I've added cal/mag to my nutes since the beginning. Not sure if I should increase the cal/mag or change the ph in case of a lockout.

Thanks in advance for any advice.

Prescription Blend Nutes week 6 flower recipe 1000ppm
4ml per gal General Hydroponics Cal/mag about 200ppm
PH to 5.9-6.0

 

[Olderfart]

PH of runoff? Given the ppm and use of cal mag, I suspect pH in the medium Rather than lack of cal/mag may be causing the problem. Worth checking anyway.

 

[Ausican]

Runoff PH was about 5.2. What surprised me was the runoff PPM of over 2000.

Since posting the q, I've flushed it to under 90ppm and fertigated with 1000ppm 6.3Ph. Now, the runoff is Ph 5.9ish 900ppm.