My sims are rapidly gaining weight in one day!

I have different problem. I play 91 sims, all of them are super skinny except one. She is not fat, but has a little fuller body shape, healthier looking than the rest. She is game generated sim, my sim married her. The rest are born in game. I began over feeding babies to see if they going to grow up chubbier. They are a little chubby until they age up to children. Then I rotate to another household and I see that child skinny as the stick playing in the park. It’s impossible to have chubby adult in my game. I see some townies have extra pounds, but not my sims.