Just wonder if anyone has had experience with a kitten who is not really growing and seems lethargic. We have two brothers we adopted around 6 weeks ago and both were playful kittens, about 2 months-old. Within a week or so the one started becoming very lethargic and felt warm, so went to vet and was told he had an upper respiratory infection and prescribed 14 days of antibiotics, which we administered. He eventually got better enough to start eating and drinking regularly, but not was not nearly as energetic or ate as much as his brother. Now it is a couple of weeks later and we went back to the vet again to see why he still will only pretty much eat wet food (will nibble on dry food to an extent), still isn't really growing like his brother (who is like a wild man running all over the house and is super-strong), and just wanting to lie around all day. The vet tested the feces for worms and was all clear, Vet also said there is no signs of anemia by looking at his gums. She was concerned about him not growing so did feline leukemia test which came out negative, but did say he had a "fever of unknown origin" and prescribed a week of c-pack antiobiotics. He has been on them two days and seems to be perking up slightly but is still just pretty much curled up on the couch and not playing or getting any exercise. It is amazing how much bigger and more energetic is brother is. His brother always wants to play and wrestle but the sick kitten wants nothing to do with it. Anybody have experience with this? Is there a light at the end of the tunnel? Do you feel the vet is doing all she can within reason?