If you dont mind me asking for a clarification. I believe Zach and I have has a similiar experience with the cat pee smell from our brute cans. The smell for me is when the water has been in there the longest. Not with newly mixed water. And if the lid is left off it does not smell. If I pick the water up in my hand and sniff it it just smells salty, even if the water/can smells like cat pee when I remve the lid.Ah - yeah, new saltwater can have a bit of sharp smell when the salt's first added to the RODI. From a chemistry perspective, I suspect that's a bit of sulfite/bisulfite. It's normal, but it's one reason I don't use mixed-within-30-minutes new saltwater, no matter what the manufacturers recommend.
I would still recommend investigating the potential questions around the specific gravity and alkalinity, since that doesn't (necessarily) result in changes to your tank.