I noticed this evening that my cat Zu can't meow properly any more. It sounds like she has a croaky voice. Should I be concerned? She is fit and well and behaving in her usual manner. But whenever she meows it sounds very different to usual like she has lost her voice and I'm worried she could be ill. She was meowing properly this morning as far as I can remember. I just wanted some advice or views on the matter. I plan to take her to the vets on Monday.