First, welcome to Pet Talk!!! I am so sorry that your girl, Sylvia is having problems. Have you changed the litter that you use? Has any of the other cats been bothering her while she was in the box? Are the litterboxes immaculate?? Cats are so fussy. When was the last time that Sylvia went to see her vet? and had her stool tested? She is a sweet senior kitty and a very pretty tuxedo. Good luck!!!