For sure... I note that Jack Keller has 2 recipes, one with just 'yeast nutrient' and the other supplemented with white grape juice concentrate. Not sure which one you're using,
@Ess-Sea vineyard ?
I am in the middle of fermenting my Elderflower sham-pagne. This year I'm using a hefty proportion of (muscat) grape juice concentrate, 2 quarts of 68 brix juice in ~3 gallons. (68 brix is ~4x concentrate, so 2 quarts is theoretically enough for 2 gallons; I made up the difference with table sugar and water which were used to extract flavor from the flowers before adding to the must).
Despite overacidifying at the outset (starting pH 2.9!) it's going gangbusters. 20g/hL Fermaid-O at 3 brix drop, but it then went from 14 to 9 brix overnight so I missed my traditional second fermaid addition. Smells and tastes great, I think it will make a great sparkling base wine.