Does anyone know about pet rats?

I'm a bit desperate posting here so please bare with me since its a bit random of a topic.

My roommate purchased a new rat from the store and she ended up being pregnant. Popped out a single pup last week and a stillborn. The single pup was very large and very chubby initially but after a week the baby has gotten very thin to the point where its making us nervous. I've been looking up about nursing the baby while momma takes care of all the other needs (shes been keeping him warm and clean). I'm wondering if shes just not lactating. I hear Human Soy Formula is the best to give a baby rat.

Would anyone be able to help me with this? I posted on a rat forum too but knowing how awesome MFP people are I was hoping someone would surprise me and know what to do.