Dogs hair

Question
We ave a 12 year old miniature yorkie. Over the last 2 months she has lost 1/2 of her body weight. Her fur is now falling out in chunks. We recently bought a Cavalier king charles spaniel and the main problem seems to have started when he arrived at the house.She eats well but only the puppies dry food as she stopped eating her own food which was chicken and rice as she has had stomach problems all her life. We are worried about her as she is not as lively as she was. Can you advise please.

Answer
Obviously, with that profound weight loss, even if she is eating well, she needs to see a vet.  If there is a systemic disease causing that much weight loss, then the skin and hair are not getting any nutrients and that's probably why the hair is falling out.