I dont believe its the temp. My rat barn is in the 80s for most of the summer. if the babies looked like they were starved, the mother might not have been lactating. Was this female one of the females that had there babies in a bin together? I've noticed when mothers have there babies together the dominant female will hoard babies and the submissive female wont nurse and stop lactating. If this female had her babies in a bin to herself, I'm not really sure. I always put visibly pregnant females in a bin of there own and have great results. The mortality rate goes down significantly. Hope I could help