We adopted 2 new kittens and they are now 14 weeks old. We've been to the vet and they are healthy and thriving, but one occasionally urinates outside the litterbox, on a pile of laundry, on the piddle pads I have under the litterboxes and today on my drapes which were "puddled" on the floor. I know he uses the litterbox most of the time. His brother has no problems using the box. Any thoughts?