I got a kitten from someone and he is about 6 weeks old. He uses the litter box perfectly fine and he is totally happy and playful. He cleans himself a little bit but not so much "down there". Yesterday he pooped and it was kind of "diarrhea like" and then of course it got on his fur on his bum and he had no interest in cleaning it off. I cleaned him myself but I am just wondering at around what age do they figure this out for themselves?