Lethargy and increased respiratory rate are not specific symptoms as they are shared with many conditions; however I’m concerned that they are a common sign that an animal is in pain, but without examining Marilyn I cannot say whether she is in pain or there is another cause for the symptoms. You should visit your Veterinarian for an examination to be on the safe side especially if this has been going on for a day or more. Regards Dr Callum Turner DVM
Thank you for your email. I do think that there might be more going on than stress, and kittens are prone to infectious diseases. If you don't trust that veterinarian that you saw, it would be a good idea to find a second opinion, even if you have to travel a bit to do so, as he could have a problem that needs to be treated. You can also call your veterinarian, let them know that he isn't getting better, and see if they have any other recommendations for him.
The Russian blue is a sweet-tempered, loyal cat who will follow her owner everywhere, so don't be surprised if she greets you at the front door! While she has a tendency to attach to one pet parent in particular, she demonstrates affection with her whole family and demands it in return. It's said that Russian blues train their owners rather than the owners training them, a legend that's been proven true time and again.