Well this may be a bit of a chore, but take out each one and check her out does she look red and inflamed smell for foul odor, sorry dont' know the anatomical names for rats. Or is there a yellowish discharge she could have not expelled all the afterbirth. The URI would make it look red or kind of scortched look. If any of them is possible I would seperate them. You can get a supp at feed store for cows, goats.... that might help with infection.