I personally use Cal-mag with every feeding, Cannabis has shown to be a very calcium hungry plant so I wouldn't cut it, did that once and the plant went nuts, besides normally when you add nutrients to your water it makes the ph drop so it's certainly not the Cal-Mag that's making your ph high, to lower it go ahead and add your nutrients to the water then check the ph, add the ph low to reach the correct ph. Now if you test your runoff and it's still high, you need to flush it with ph balanced water until it reads the correct ph. Hopefully, I answered your question and remember Happy Growing and Free your mind one puff at a time.