[Mozart's Mom]

Hi all. My Mozart is a 4 year old male Rottie who has been obedience trained and house-broken since we got him at 3 months old. He has been the perfect dog in every way. About 2 months ago, he finally started lifting his leg to urinate instead of squatting. However, at this time he has also started marking in the house. When I correct him, he knows he's done something wrong, but he's kept doing it so four weeks ago I took him to the vet and found he had a bladder infection. We've treated him for it and it's cured, but the vet mentioned in the results of the tests we had done that he has a high PH level, due to the food we're feeding him, which will make him prone to bladder infections often. During the treatment and for a few days thereafter, Mozart was pretty good at not going in the house. However that was short-lived and yesterday he lifted his leg on my bed right in front of me! Has anyone had any experience with a previously trained dog straying from good behavior? Should I re-crate him until he re-learns what is acceptable? What type of food would lower a dog's PH level?
Any and all suggestions would be GREATLY appreciated since I love my boy but I want him to behave.
Thanks,
Mozart's Mom (Candy)