Can worms make a kitten feel so bad they are not playful?

We adopted 2 kittens from a rescue last Sunday. They are approx 7-8 weeks old. The boy is much bigger than the girl. She is very small and is not playful at all. He is a crazy boy chasing anything that moves. She is eating pretty good now but still is not playful. She is very loving and will find us on the couch and jump up and climb in our laps. I took them both to the vet yesterday and she is only 1lb but gums are pink. They were both dewormed and will go back next week for another dose. Can having worms make her not playful? Do cats generally feel bad when they are infected? Anyone have a cat that was very small and sort of lazy that turned around and became a healthy cat after getting rid of worms? The other possibility per the vet is a congenital liver defect. A mom cat may have shunned her if this is the case but the babies were rescued at 1 week and bottle fed until they could eat wet food.