They've had a young/pregnant/elder rabbit formula for a long time -- I know it was around when I started rescuing about 5 years ago. The rat formula is not appropriate for babies, and there is not a young rat formula, maybe you got them mixed up.
We are as gods to the beasts of the fields. We order the time o' their birth and the time o' their death. Between times, we ha' a duty. - Terry Pratchett.
"Men have forgotten this truth", said the fox, "But you must not forget it. You become responsible, forever, for what you have tamed. - Antoine de Saint-Exupéry