Dirty Butt

My 7 week old girl from the pound uses the litterbox very well for her age, but she doesn't clean herself afterwards and you can see some leftovers on her bum. Is cleaning one's self something that comes with age or will she always walk around with a dirty butt? A stupid question, I know, but I have never had a cat that wasn't obsessed with cleaning themselves.

Lately there have been a couple of threads about this subject. I have two boys that think it's totally okay to sit on my pillow after they poop (YUCK!). I've been wiping their bum frequently with a wet paper towel. Immediately afterwards, they start licking their bum, I think because there's water there and they want to clean it off. I try to catch them immediately after they have a bowel movement as often as possible and I think they're getting the point. The sheets are cleaner anyway.

What has helped the most for me though is to get them better food. I posted something about this before. I aimed for firmer stools, which I believe is directly related to diet. There's been much less mess.