I have an elderly cat who is about 15 years old. Vet says she is in good health. I just want to know what is normal behavior for elderly cats. She is relaxed and sleeping most of the time. Her favorite spot right now is on our mat in front of the oven. Her appetite has decreased. She often makes a sound like she has a hair ball but just a little clear liquid comes out. Are these normal things for a cat of this age?