one of the biggest things in coco is to remember thats its NOT hydro, and its NOT soil. it has its own requirements and quirks. if you ph to 5.8, you're going to have bad Mag problems. you want to ph to 6.1. if the maker of your coco pre charges it, you can pretty much use it without worrying about anything, if they don't you not only have to give it extra C and Mag, you have to be aware that once its full, those things all of a sudden become very easy for your plants to get, as the coco will quit absorbing it. that usually happens about the third week of flower. (at least in my experience) pure coco is very heavy, even though it has excellent aeration. i like to mix in at least 30% perlite to aid drainage.