Carbonate hardness comes to mind when discussing alkalinity and ph, at least in coral aquariums. Might help here. Here's a definition:
" Carbonate hardness also known as KH, refers to the concentration of bicarbonate (HCO3-) and carbonate (CO3--) dissolved in water. Hydrogen carbonates are easily soluble in water, while carbonates virtually insoluble. The level of carbonate hardness thus depends on the amount of dissolved hydrogen carbonates.

Carbonate hardness affects plant growth to a greater extent than does the level of non-carbonate hardness. Plants can dissolve carbon dioxide out of hydrogen carbonates and use it for photosynthesis."

So, there's interraction between the metals, minerals, bicarbonates and carbonates in an ion power struggle for control of ph. Good thing you don't have to add nutrients, and really make it interesting, lol. Just kidding, but I sure do appreciate the simplicity of growing in soil. :jointsmile:

After keeping saltwater tanks, and all the care and coddling, testing and adjusting (and cost) that goes along with it...the last thing I want is to do is overcomplicate cannabis, too.