my oldest cat Audrey is 5 but over the weekend she has started doing her business on my living room rug. ive cleaned it up and shes done it again. I have 2 litter trays both clean and my other cat is using her tray fine. whats wrong???!!! ive cleaned it again and sprayed some behavior spray on the spot to deter her but she still hasnt been in her litter box today??? advise??? 