It's mag. Doesn't nes need cal. So, a Epson salt feed would be a great quick source of what's needed. Add enuf to that'll it add 150ppm to your water. So, if your tap is 100 your feed should be 250ppm. If you're going to use epsom salts.. make sure it's pure. As a lot have lavender, or menthol. It'll just have mag/sulphate as the ingredients..
Coco 5.5-6ph.... 5.8 been optimal for coco.
Soil. 6.2-6.8.....6.7 been optimal for soil.
Good Growing.