my calico is 16 almost 17 years old. I have 3 male cats, one 3 year old and two 1 year olds. The senior for the past 2 or so years has increasingly exhibited bahavior changes such as eating more frequently without gaining weight, not grooming as much or often, and she tends to hiss, growl and cry an awful lot with the other cats and humans. I am not sure what to do for her. Is it time to put her to rest?