7 is ok, but just that... ok, you need to try to notch it down to 6.5 with the coco. i haven't tried coco yet, but i know others who have, and they had to use ph down to get it straight. presoaking is supposed to help too.

over watering shouldn't be a prob with coco, as it dries quickly, but you may not be watering enough. my friend waters three times a day, like a hand watered hydro system.