I'd also be hesitant to give yogurt to chins since they're vegetarians -- the lactose may upset their stomach even more! You can buy acidophilus capsules at most drug stores that will do the same thing.

Yogurt is not a problem
It's best to use products like zoolac or things made specifically for rodents, but if there's nothing else on hand, and it's real bad, yogurt can be used

I'd just rather not chance it when you're already having stomach problems. It's a sugar and not well digested by rodents in general. They're vegetarian animals and not designed to digest animal proteins like lactose. It's like giving them a big glass of milk.