So, I have a litter of 4 kittens, they are 8 and a half weeks old, and I've noticed the youngest one is acting strangely when compared to the others. Her name is Dawn, and she's a little siamese-tabby looking mix. She is by far the smallest one of her siblings. While the other three are always playing with each other and running around, she only ever just sits in her little spot she's claimed and sleeps or just stares off into space. She also has a very slow reaction time, and doesn't respond as quickly as the others, and doesn't seem as smart, as she has trouble remembering things I've taught them all to do to get treats that all the others catch on with and understand. She has very little coordination, and will topple over or stumble very often. She doesn't eat as much as the others, and is very small and light. She also doesn't meow very often, only if she is hurt. For example, she wont even meow when she's held upside down, she'll just lay limply and not even try to move. She does seem to have normal body proportions for her age though, even though she is very small. I'm not sure whats wrong with her, and would appreciate some help on the matter!