Brush their teeth. You can use a human child toothbrush with warm water. Or you can get a kitty toothbrush and cat toothpaste from the vet or maybe from the pet store. Don’t use human toothpaste. You can get cat treats that are designed to help remove tarter from their teeth. If you start brushing when they are young, it’s not as hard to get them use to it.
Also check their gums and make sure none of them have bad teeth. Their gums should be a nice healthy pink, not white or really red.
If it’s not their teeth, then it could be something they are eating. If all of them have the same stink on their breath, and it’s not their teeth, then you might try changing out their food (slowly) to something else. If that makes a difference then you know which food not to feed them.
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