I grow in coco and a mix of clay balls,you need to add something like the clay or perlite,because it becomes,that wet that the plants will find it hard to get air from just the coco.the tap water that I have is around 7.0 ,but I no longer ph all I do is make sure the plants are getting the feed they need ppm/ec start them of on 1.1 ec.it is also well worth useing something like a cat litter tray to start them of in,with just clay balls in the bottom of small pots coco clay ball mix in the top.put some kind of cover over the tray like the cor agates board ya get when not growing or just black weed barrier over the top of the tray with holes cut in it for the pots,put a good fish tank pump,with a splice in the tubbing so it will take two flat air stones,make sure the air stones are covered and the pump is putting plenty of bubbles in the tray,this is a great maintanance free way of watering,but don't add the stones till the roots hit the bottom of the small pots,I have had plants grow 5 ft tall in a 1 litre pot in this way,by doing it this way it's not the pot size that matters because the plants will uptake the nutrients they need just via the roots,with the coco just been a medium to hold the plants up straight,give it a go.
