Using coco you are growing hydroponically, you'll feed every time you water.
When small, watering I do daily, but in small amounts to get the roots growing, by the third week I'm feeding every day till run off, and twice a day mid flower on.
Coco you do not let dry out. It becomes pretty hydrophobic.
pH is fairly critical, and drops with a color chart will not keep you close enough. ( that said, that meter set is junk.)
No idea of the space you have available, unless your starting small strains, 9 seems like an awful lot under 1000w.