I've used these powders.
They are very potent.
Also, you can't go by Grams per L. Depending if your water is hard etc.
Also, you are PH'in these solutions right. Ph from these powders are in mid-low 6, for my water anyways.
Start adding higher PK. But looks like it's ph related. You are flushing out that coco weekly to avoid salt build up.