i didn't see anywhere if you washed and presoaked/buffered/charged your coco
i usually first rinse the SHIT out of it, (warm water) over and over (i use 1/2-1 block compressed, crappy pyth coco called gro block or something)
then i submerge it, and add an air stone (optional) and add 3ml cal/mag a gallon. now i ph adjust down to 5.0
the ph goes up each day, on the 2nd or 3rd day depending on the amount of water used, it should be up around 6 or 6.5 (or at least higher than 5) you can bring it to 5.8 and wait a day (optional
now i swap the water with fresh water and add the same cal mag dose and 1/4 dose nutrients and ph down it to 5.8
its really hard to dry out so i try to squeeze most of it out and then use it. I've considered taking buckets and putting holes in the bottom so i could use it as a huge strainer into maybe a kiddie pool or something. Right now i just do it all in a bath tub in buckets (PITA)
the reason i add the nutrients along with cal mag is my nutrients don't have enough cal-mag in their formula to fully support the plants. the 1/4 dose sort of gives it a base nutrient and also helps with coco leeching nutrients out of the waterings because it will naturally lockout cal-mag
i also leech the coco once a month with 3x the medium size of water, to avoid salt buildup. a 2 liter bottle would get 6 liters of water ran through it. this cleans out the root are and eases nute uptake . ALWAYS try to match water temperature with temperature of the medium being used, should always be 60-70degrees. This avoids shocking the plants.
in addition to leeching i do a runoff method, where i do first watering "full dose", next watering "half dose", next watering "1/4 dose". Each watering gets about 10% water to runoff so i'm sure that i'm keeping everything nice and fresh, and controlling the pH and ppm's of the coco by constantly running just a little extra through, controlled.
i find silica and carbo additives are great too. My nutes used are Dyna gro; Pro-Tekt, foliage pro, General Hydroponics Calmag, humboldt honey hydro carbo load. I use KLN by dyna grow for transplants and clones and it seems to work