cocco is well known for causing ph issues if not treated properly before planting, judging by your pics I would say that that is a ph issue, I ve never personally grown in cocco but Cultivator is a cocco gurru, he can tell you what the process is for treating cocco before use, I think you soak the medium in ph adjusted water for a period of time, hope this helps.i was under the impression that canna coco was sposd to contain no additives, and their website suggests the same:
"CANNA Coco substrate is a 100% organic product having a fine, uniform structure, free from viruses, chemical additives and soil diseases. The fact that CANNA Coco is not steamed is not the only thing that distinguishes it from other substrates; this is also achieved by the use of pure, first class source materials. Which come from India, where CANNA’s production facilities use fresh water only to soak the coco. This to make sure no salts gets in contact with CANNA Coco, ensuring a clean product."