Kitten throwing up?

Our kittens are 4 weeks old, still nursing. Last night one of them started throwing up, probably about 4 times since last night. Anyone know what might be the problem? He acts fine from what I've seen, just suddenly throws up, never happened before.

Worms??
I would definitely take him to the vet!

Well, another one is throwing up too. It's gross foamy white-ish vomit. I'm taking them to the vet. Should I take all the cats in (we have 3 adults, 4 kittens) to check them too?

Nevermind, I called the vet, they said to just bring in one of the kittens, and they can tell me what to do for any of the others that show signs of it.

Well, the vet said he suspects distemper, not good. He gave us some ammoxicillan to give the sick ones twice a day and hopefully it's just a little bug they caught. I really hope it's not distemper, cuz he said they normally will die from that. None of our cats have been vaccinated and they are indoor cats but one has gotten out a few times in the last few weeks, so he says she probably brought it in.

Well, the medicine seems to be helping. They haven't thrown up anymore and are more active today, so my guess would be it's not distemper

Sending good your way! Keep us updated!