Too little calcium in early flower?

looks like a calcium issue to me, with hints of magnesium. No idea whats the NPK breakdown of coconut water power is but guessing not a lot of Calcium as the label did not say on their website. May also want to update your diary with more information on feeds and how much your giving them. try and get the manufacture to give you a proper NPK breakdown and all other micros in the products. If they cant, maybe time to find a new brand. Good Luck!

Perhaps not calcium but magnesium. Since Cal-Mag is the likely fix it will cover both bases. Last year I ran nutes on Sundays and Cal-Mag on wednesdays, since the imbalance often swings like a sine wave as the chemistry of things runs it's course. If it's locking up, you will see it in the PH of the soil and the runoff after watering with pure 7PH RO water or a bottle of 'distilled' water from the store is even better, as it will counteract whatever is buffering you.