best runoff EC before harvest for taste in coco / leaving the plant use its reserves ?

In general the last 2-3 weeks are considered ripening. During this period providing only PK for 10 days is recommended by many growers and manufacturers. The last few days are left for flushing with special components for dissolving the salts accumulated in the substrate. This is made to specially cause active nitrogen deficiency. It forces the plant to break down chlorophyll and use all stored nitrogen in the leaves. Still debatable, but it’s believed that result is the boost of sugar production. That’s why GHE for example advises using only Ripen with no other additives for the last weeks of flowering.