Dogs now on Royal Canin SO Urinary food-questions

Jesse had blood and crystals in his urine but no stones. Jake had blood in his urine with bladder stones. For now they have been switched to the Royal Canin SO Urinary food. A couple of issues-food serving is more volume than they are used to so it's hard for them to eat all of it. They are also much thirstier (food is designed that way) so they are drinking much more water, which I am sure is suppressing their appetites. I'm not worried so much about Jake-he is 66 lbs and overweight. However, Jesse was dead on at 50 lbs but has lost 2 lbs in the two weeks he's been on the new food. He's always been cyclical in his eating habits but right now is far more interested in just water. It's a struggle to get him to eat. Had an appointment today for a skin/thyroid med follow-up and the vet indicated they both should adjust to the higher sodium level therefore the urge to drink water will subside some. Has anyone gone through this? Vet also indicated that there are other foods to put them on if this one is causing issues. Comments? Thanks.