Sulfite helps the developer to develop faster, so when sulfite is reduced, density will decrease, even at the same pH. You need to develop longer if using low sulfite.
Originally Posted by Relayer
6.3 g of Borax has the same number of boron atoms as 6.7 g of metaborate, but it has much fewer moles of molecules, so I think buffering will be worse. I suggest increasing acid and alkalis to improve buffering like this:
sulfite=90, ascorbicAcid=9, borax=10, s.carbonate=??, phenidone=0.1
Adjust s.carbonate to give pH=8.3. More than 10g of borax would be better, but it might take too long to dissolve.
The left scan in your images looks like the scanner was slightly out of focus. It is difficult to focus scanners accurately to measure grain. Can you re-scan that negative with manual focus on that part?