Coco, as we know must be supplemented with calcium and magnesium. Initially, coco needs to be buffered with a calcium and magnesium (CalMag) solution. It has also been my experience I need to occasionally (actually quite frequently) supplement with CalMag throughout the grow. I also use Jack’s 321 nutrient feed schedule. Calcium is derived from Part B - Cal Nitrate and Magnesium is provided by Epsom Salt.
With this as the backdrop, does it makes sense to add something like Langbeinite as a base source of Magnesium with the added benefit of Potassium (soluble potash) and sulfur. Likewise, can pelletized gypsum be added for its calcium. Bruce Bugbee adds it to his peat mixes at 10g per cubic foot.
I thought I would throw this out there to see what you are doing. I am currently preparing 40 - 50 liters of coco and figured now is the time to add to the mix.
all will be appreciated