:smoking: sorry for the delay mate, I just did not get that tag, and have been busy elsewhere,....
....You say it's stopped now? I suspect a pH hiccup that corrected already.. that particular necrosis/yellowing looks a lot like what happens in hydro when pH drifts suddenly, and in coco, you're closer to that than true soil by miles,... That said, Nammy is right, your water is hard enough to really strain the AN nutes buffering capacity, which BTW works only in solution, not once in the pot/root zone.... Are you confirming the pH before going in? Are you testing the run-off for pH and ppm's? this is pretty nuch required with coco, and doing 15-20+% run-off each time,.. never wtaer alone, etc,. etc.... a lot of do's and don't's in coco!
Good luck man.
