Nutrients deficiency, sulfur,potassium and cal-mag...

I feed when the pretty dry the GG hate over watering and I usually let about 10 to 20% drain out of the pot. The ph is anywhere between 6.4 and 6.1. I have it going in at 6 to 6.2. I did flush. But I'm thinking the same . Also I'm using botanicare cal mag at about 5ml to 7.5 ml per gallon. Should I have it at 15ml per gallon. I couldn't remember What I used to uses. And I have been using mexican bat guano at anywhere from 8 to 10. On the npk. Since I'm using raw ingredients in my compost brew. I like to get away from the bottled cal mag and use the down to earth azomite but I can't find anyone who's used it reliably and has some good product from. Also I did hit some of the GG with sulfate of potash magnesia at about 5% on th k 2.5% on the magnesium 5.5% sulfur And they are still yellowing up. Looks like the botanicare is at 1.2% magnesium At there recommend dosage. Do at most I gave them only 2 to 3 % magnesium per feeding. So I'm thinking you might be right about the magnesium.