I two little chihuahuas that I love dearly. I notice my apartment started to smell like dog pee but could not figure out where they peed. I moved my couch today to realize that they have been back there peeing. These are very old stains on beige/tan carpet. I have removed them some with laundry soap and water and shop vacuumed up the water which got the dark yellow out but you can still see it. Is there anything I can so I don’t have to replace my carpet?