pests? Abnormal ph? k def? Or maybe just too much "stuff" sprayed over the leaves too often? And in coco known for its own problems.

I'd certainly stop foliar spraying your crunching leaves and adding to the problem. Then I'd start looking around for someone who works in coco because that looks like a ph/def issue (unless it's pests just attacking one part of the plant which would be even more odd) and figure out exactly what your ph should be and what it is.