Regarding rockwool: As long as its not for the seeds its mold proof. If the seed is big and your rockwool cube small enough it will come with the energy stored to make it through the rockwool cube telling you you should plant it if you havent yet, or make it through to the soil. If the seed is small or your rockwool cube relatively large you must feed it with any kind of nutrients may it be compost tea.
Adding more perlite sand and mineral matter might improve drainage and with it reduce dampening off but require more frequent watering.
I recently had a booklet from a coco cour supplier, they describe all the goods and bad theyve came across when researching coco, one thing is sure: Its a completely new and different media and traditional approaches must not always be right with coco. So being a matter of its own its also an investigation of its own. No se