My kitty, slinky used to always use the litterbox and up until about a week ago she stopped. Now she pees on everything especially my chair and she waits when I'm not watching and then goes on carpets and rugs a nd somtimes my chair. The litterbox is clean and my other cat has no problem using it. But slinky refuses to uses it and i have no clue why? Please someone help me figure out how to improve this.