Are the new chins quarantined in a separate area of your house, away from your previous chins?
Yes, new chins can upset a previous pair of chins and cause them to fight. If you found fur, you need to separate them before it becomes worse and they end up doing damage, or even killing one another. Check both of them over for bite wounds. Blow in all of their fur, it helps you see the skin that the fur could be hiding.