I have 2 11 year old female Westies. Over the last few months, one of them is peeing in the house, either at night or during the day when I'm at work. I have worked very hard to take them out often when I'm home and during the day when I'm at work they have a doggie door to get outside. They used to have run of the house, but then I was finding areas (under the bed, bathroom rug, kitchen rug)where one of them peed. So I then limited them to part of the house, but one of them is still peeing. It's at least 3-4 times a week. I can't figure out which one is doing it. Nothing in their routine has changed (schedule or diet). I even had their urine tested for a bladder infection and that came back negative. Other than locking them outside, which I don't want to do, I'm running out of ideas. I'd rather not put them in a crate because they've never had to do that and I hate to restrict them. Other than putting up camera's to film them, I'm running out of options. Any ideas or thoughts of what I may have missed? Thanks for your help.

It could also be the age 11 years its long way in dog life