Marks on leaves

Es una pequeña deficiencia de Calmag. Agrega a la solución un poco mas de calmag y no deberias tener problemas.

Developing calcium deficiency.

Calcium. The rest was explained by person whom i would ask advices how to grow in coco .

With a feed around 1.2-1.5EC you want 100ppm or more of Calcium.. anything less will result in a defiiciency. It needs to be part of the fertilization at all times.. not because it is coco, but because plants need it at those levels. Bad coco can leach out Ca, but that is a temporary situations until it reaches equilibrium with your feed. This would normally be accomanied with a salinity toxicity, which i don't see here. Give more Ca, one way or another witout causing an imbalance somewhere else. 1-1-2 NPK ratio and 4-2-1 K:Ca:Mg with ~100 ppm S at a total overall concerntation of 1.2-1.5EC ... higher with supplemented CO2, aweome VPD and a shit ton of light. These are ballpark suggestions that require trial and error to fine tune to your environement, but i guarantee it'll be very close to ideal. Every person that understands and follows my suggestions with good soilless/hydro nutes has great results their first full cycle doing it this way. After that you can play mad scientist and experiement all you want and have a healthy baseline to compare to. Proof is in the pudding. Get a "real" agricultural company's fertilizer, like Jack's hydro 5-12-26. pair it with Calcium Nitrate. Maybe get something to boost P, but the base 2 products is all you technically need. pH buffered, pH balanced, 100% soluble and 100% plant ready fertiizer. In coco yoyou fertigate every single irrigation and get 10% runoff waste. Do that and it is easy sailing.