I am not a fan of foliar feeding, because a.) that's not how plants typically absorb these types of nutrients (assuming they are absorbed at all), and b.) I don't want anything on the surface of my buds that the plant didn't put there. But I know many experienced growers do this and claim good results, so it's just my personal preference. I will say this however, humic acids are produced in the soil via organic degradation, and are beneficial because they have unique chemical properties that allow them to form bonds with minerals such as Mg, Ca, and Fe. They form complexes with these mineral ions called chelates, and these complexes are what allows proper and efficient absorption into the roots. Humic and fulvic acids are definitely good amendments to growing any plant, but I think you're better off either using soil rich in these compounds, or amending it with soil-based nutes like Budswel or Big Bloom, which are loaded with them. Just my 2 cents.