Kitten 18 week old changes in her behaviour

Hi I've recently adopted to kittens bro and sister they both been playful both eating fine etc but I had my eyes on the female she only eats dry food drinks more water and her coat don't seem as soft as the male and tonight I've come home and she just don't want interact with anyone just sitting in corner she won't play with her toys does this sound firmilar is it something to worry about? she was eating well this morning any ideas anyone

They are both booked in vets for 1245 for there first check up and injections well maybe not injection for Molly maybe not Grr last thing I needed

Sounds like she might have a little upper respiratory thing going on, which is very common after bringing kitties home to a new environment.  Definitely hold off on any kind of vaccines until 100% healthy.

Well I've noticed her tail is down and won't lift it if I rub that area she wiggles her tail other wise she looks in real pain gripping to covers etc