It has not much impact. The acidity is given by the phosphoric acid. 0,425 g in 23 l is as calculated 0,018 g/l. What means it is 0,018 g/l/98 g/mol = 0,00184 mol/l . Assuming we talk only about the first Hydrogen of the Phosphoric acid it is 3,7 pH. Your wine has already a pH 3,5, so there will be not much change. The D acid is a weak acid and give a pH of 4,75, if assuming 100% dissociation what I don't believe. I don't have pKa value at that moment.
PS: Do you work in Napa valley?