My two cats (who I've had since kittens) were indoor cats for the first year and a bit of their lives. They do go out now but only when I'm in and when it's daylight so they're still pretty much indoor cats. I've always fed them 1/4 of a carton of Bozita each for breakfast and the same each for dinner, that's the approx equivalent of two pouches each a day. On top of that they have a bowl of biccies down 24/7 but they don't tend to eat that many biscuits. The bowl probably lasts 3 or 4 days at least.
So mine have approx 200g of wet food each per day plus a handful of biscuits. Your girls are having 100g a day each of wet + biscuits. I guess it depends on how many biscuits they're consuming, could you try weighing out set portions of biscuits to see how much they're eating biscuit-wise?