Kitten not playing

I have 2 kittens, Munchy is 6 months old and Hidie is 7 months old. From the beginning Munchy plays non stop and eats twice as much as Hidie. Hidie, I think is the Alpha cat. Hidie has never been a very active cat but I notice lately she is not interested in playing much at all. She was sick for a few days recently but now she is better. She will play a little with Munchy but will not chase a ball or bat anything. She only wants to be held and petted. She is a very vocal cat and "talks" alot. Is it normal for a cat of this age to be so lazy. She is also small for her age. I am trying to help her gain some weight. I have never had a cat that is so loving and sweet. I just want to know if this is normal. Every kitten I have ever seen is so playful.

It's not usually normal for a kitten to be that way at that age - however I have a cat that was always an exception (and is still a very lazy cat).
If Hidie was playful before she got sick and less so after, chances are she may not yet be feeling very well. Has she had another check up with the vet to make sure she's better?