I actually had a talk with the horticultural guy (has some sort of degree if that means anything) at my hydro store about this topic specifically. It's my understanding through his opinion that alot of nutrient companies don't even know the proper dosing for these. Specifically when to use them. For example I use GH Flora, and in their nute schedule they say diamond nectar during veg. The bottle says its humic acid which is good for veg, however guy says this is actually fulvic acid and is suited for flowering. He brought this infomation to the attention of the General Hydroponics rep specifically, who had no answer for him, though didn't disagree with the logic. He did try to explain the difference to me, however I found it somewhat confusing, but he definitely mentioned this specifically which I also found quoted in the Humic acid wikipedia: "fulvic acids are humic acids of lower molecular weight and higher oxygen content than other humic acids."
With that in mind what I took away from my conversation with him is that humic and fulvic acids are beneficial, however you have to know whats really in it, and not necessarily follow the schedule as described by the manufactuer. Humic acid is suited for the Early stages of growth, and Fulvic for the later stages such as during flowering.
With that in mind, Diamond Nectar is the only item in the GH feeding schedule I don't use, but I do use a 3rd party humic acid that I also got as a free sample. Not sure what I plan to do if anything in this regard when the sample runs out. I keep my nutrient feeding schedule the same, and mess around with suppliments. Not sure if its helping, but doesn't seem to be hurting. I beleive these chemical compounds are supposed to help the plant absorb nutrients in general.