Nice discussion here, and bigsmo, nice looking plants despite the issues.
Fwiw I'm using 45 ppm ro water and 5 mls/gallon Botanicare cal mag(max recommended dose), using COBs of course, and not having the cal mag probs. This is on my youngest girls only, as I was using 300 ppm tap on on older girls with less cal mag. Always had cal mag issues on every grow. So far so good on this latest grow. Also if I remember right, probably not, but I think excess potassium can lock out cal/mag. I'll have to re-research.