I would never add grains to my coco. Grains mold faster than just about anything. Seems like a great way to cause root rot or a fungus infestation.
I use humic acid in my nute mix without any problems. When I tried using Fulvic acid in my nute mix, it just burned the crap out of my plants. When I use Fulvic as a foliar spray, my plants like it. Fulvic is strong stuff, be careful.
ya know giving it some thought...fulvic and KSi might be good to use together in a foliar solution to get the PH just where you want it...given they are an alkaline and an acid.
The BioAg stuff out of OR...has a liquid bottle that has the good ratio of humic and fulvic together..I think I'll see how they are with email questions.