At fist glance and with my decades of experience, I would say it's a calcium deficit and your best options
Make sure your pH is balanced, re-apply a new nutrient mix if necessary.
For Coco: Ensure Coco has been buffered with Ca/Mg. Without buffering, Ca and Mg deficiencies are more likely to occur.
Organic Solutions:
• Egg Shells. When crushed in soil, it will a be a slower release. However, crushed egg shelled, warmed up, mixed with vinegar (1:10) as a foliar spray will be a much quicker way for your plant to recieve calcium
• Dolomite Lime
• Organical Magic
Inorganic Solutions:
• CalMag Supplements
• Calcium Nitrate