I'll see if I can get them to the vet and see if there's something serious going on. But I find it a bit strange that I'll find a stain only when I come home from work. I had forgot to shut the bedroom door yesterday when I went to a funeral and I was gone for a couple hours...the bedding was still clean when I came back. And they didn't go later on that night when I was at home, but playing video games with my brother in his room for a few hours. Kind of makes me wonder if there's really something serious going on or if they're trying to tell me "I am SO displeased with you! Take that!"