Coco is Hydroponics. You must feed with every watering to 15% - 20% run-off. You do not need to fertigate every day when the plants are young but never let it get dry. The whole idea behind using coco in the first place is to be able to fertigate several times a day to keep fresh "In Balance" nutrients at the roots constantly without it becoming soggy. Start fertigating 2 hours after lights on and stop 2 hours prior to lights out. By the end of the fertigating cycle you want that 15% - 20% run-off.
Read about balanced nutrients here and why it is so important to use a complete Cannabis nutrient line.
The proper use of “salt” based fertilizer to grow Auto Flowering Cannabis. Salts: Natural and man made any chemical compound formed from the reaction of an acid with a base, with all or part of the hydrogen of the acid replaced by a metal or other cation. Learning how to use salt based...
www.autoflower.org
Ps. I have never seen a good grow here with a 80% coco/ 20% soil mixture. I have seen 80% soil to 20% coco work; where the coco is used to lighten the soil but if you go more coco than that it will not work out well.