Does she cuddle with her siblings when mom isn't in the box? She could be crying because she is cold. Is she gaining? Are they weighed everyday? This is the best way to tell...because they can gain such a tiny amount everyday it would be hard to catch that or even a tiny loss without documentation. I weigh them at least twice a day...am and pm. She should be gaining everyday a loss or even no gain and just holding her own should be watche very closely. I have a scale that does grams or oz's, in the beginning my tiny one had to be weighed in grams (most accurate) because it could tell me if she even only gained a couple of grams between feedings. Hope this helps