For the same reasons of needing to lower nitrogen later in flower, i started using calcium ascorbate in addition to calcium nitrate. As flower progresses, the calcium nitrate decreases, and the calcium ascorbate increases.
With a solubility of 50g/100ml, it is much more soluble than calcium sulfate. And imo, we do not need anymore cations paired with sulphates in our nutrients. It is 9.4% calcium. Hydrobuddy calculates 4g calcium ascorbate for 100ppm/gal. I purchase pharma grade powder on amazon, relatively cheap.
To keep my sulphur in range (30-50ppm), i like to also use magnesium ascorbate in my formulation. By adding multiple combos of cations/anions into hydrobuddy's substance list, it helps the dreaded "gross error" warning.
I've noticed some of the new nutrient lines are touting carbon, and they're getting it by using citrates, due to their high carbon %. Not at all sure if the plants are getting anything from this form carbon, so not making any claims, but ascorbates are higher in carbon than citrates. Calcium ascorbate being 33% carbon.
Bruce Bugbee says he likes to use vansil 10 for Si. It is calcium silicate, so it too, could chip away at the calcium nitrate, as well as add Si.