Jen my heartfelt sympathy to you. I know you will do your very best to solve this problem and it is indeed a difficult one. I worked with a girl once who had ONE cat that was constantly spraying in their basement as he aged. The pee was permeating the concrete so badly that after the kitty left for the RB they actually had to break up and replace the concrete in order to get the odor out. I certainly hope you can get things under control or that you will discover one day that this has all magically just stopped.