Hey
blondie. I have some Ace Malawi purple line growing now. I used the mix similar to what Dubi recommends, about 6 parts Pro Mix HP BX, 1 part loose coco, 1 part worm casting, and I sprinkle a bit of guano in the bottom 1/3 of the pot. I have never had healthier looking plants, I really like this mix. Yes that looks like mag. Potash and magnesium compete with each other for uptake into plants, too much of one blocks the uptake of the other. I think your problem honestly is the espoma potash. That is derived for muriate of potash. Muriate is a common commercial fertilizer, our farm spreads it on our fields, it is a great source of potash. We also use it as part of a corn starter that we place beside and below the seed when we plant. The problem with muriate is that it is salty, and in coarse ground like our sand fields we have to use less than our clay or we can see salt damage in the corn because the salts can move easier in course soil like sand (or growing mix). Cannabis will be the same, a bit of muriate in the soil will be ok, too much can fry your plants, which is likely what happened to your first one.
I use a blue lab combo meter for pH and EC and have had it for a few years. I tried several cheap pens before that, they are a complete waste of time. The blue lab meters have gotten ridiculous in price though. They have a pen for just pH that is much cheaper than the combo meter if you only want pH, I haven't used it though, just seen it on amazon so I'm not endorsing it but I am happy with what I have. I also just feed with a standard liquid line and they seem super happy being fed around 0.6 EC going into flower. I do think the issue is the potash though.
