Nah I usually get a pre buffered bag of coco
Prebuffered coco doesn't mean it is buffered like soil - it is prebuffered to keep calcium cation exchange because it is an inert medium ….
So as you continuously water thru it without maintaining this important balance - things happen.
You would have been better off running it as hydro.
Using salts instead of granulated “ soil “ fertilizers.
DTE fertilizer is designed for soils that have organic elements to be broken down over time - where as coco and salt based hydro nute will keep the important calcium / magnesium balance as it was when it was prebuffered. Bonding of those elements to the coco.
The cation exchange sites in coco will strip the nutrient solution of the Ca and Mg and replace those cations with Na and K. This creates a sub-optimal Nutrient Element Ratio (NER) and renders Ca and Mg unavailable to the plant.
As stated before - coco / dry fert grows createtoo many variables.
You would have been in a better place if you started your grows
in soil or Coco as Hydro.