Well my k def was actually a result of fert buildup in the medium.....locking out the K because believe me I had a TON of K in my nute solution. But since you have said that you have done a flush I am less inclined to think that in your situtation now.....espically after discovering you are actually doing the opposite treatment we talked about.

I think you using 3/4 RO water has caused an MG def amongst other shortages and I'm pretty sure that is your problem. That's why I suggested going back to your regular tap water.....and was rather surprised when you mentioned that you were now using even MORE RO water.....but still no CalMag instead of going back to your tap water. You may have squeezed by with enough calcium and mag etc in your tap water.....but you certainly aren't going to get any in your RO water so I'm sort of wondering why you didn't start CalMag when you went to RO water....it's pretty standard to do so and most people who use RO and DONT use CalMAg WILL run into problems.