To be in the reduced form, sulphates need to be in the correct Eh & Ph range. I believe @john.kempf said that 3% fulvic acid weight/vol to total nutrients weight/vol is enough to chelate everything. I have had very good success this year chelating sulphates using fulvic acid. I used LAB ferment as the reduced medium to add the sulphates and fulvic acid too.
The Eh reading below was from a mix of sulphates, soft rock phosphate, gypsum, seaweed, humic mixed with LAB bioferment and some added water. Fulvic acid was then added to chelate in this reduced state.