What could be making my kittens puke?

They're otherwise healthy, but 2 of Pennie's babies have been puking, mostly white, curdled milk. They still nurse quite a bit, but eat some solid food, too. As far as I can tell, it's the 2 girls, none of the 3 boys who are getting sick. What's up?

over eating? Maybe the food does not agree with them? - Has moms diet changed??

Thanks for your quick response. Of the 5 kittens, the 2 girls seem to eat the least. The boys are good eaters, but not the girls. I just changed (am slowly transitioning) their food, because mom's poops have been so soft and on the verge of diarrhea since I got the food I'm transitioning from. Hope that makes sense. It seems like kitten food is too rich for her. The babies are 8 weeks old. They've been pecking at mom's food since around 4 1/2 weeks old. The vomiting has started in the last week.

I think its the change of food in moms diet. I could be wrong but that is what I think. If the kittens are throwing up a lot, Id take them to the vet.

Cuddles was doing that and I took him to the vet. He was puking food and curdled milk. He was also constipated. The vet said it was the transition from milk to food. He's not doing it now.

Is anyone (mom or babies) getting cows milk by any chance?

Noone's getting cow's milk, but sometimes Pennie gets a few scraps that dropped to the floor under the table. She seems to have a sensitive stomach, as she almost always has soft poops, and many times it's runny. I haven't noticed anybody getting sick today.