That is so sad and sorry to hear.

My first thought was that you may have brought home a new animal but you already said you didn't.

We didn't have enough rats once and my husband brought some pups to feed but one of the snakes didn't eat it so we put it in with a nursing mother and my entire rat collection died within a couple of weeks. We are pretty sure we got that one sick pup and that was that.

I hope you figure it out and everyone else stays healthy. Good luck!