I'm taking a guess here, but it may also be that you're parenting three different versions of your daughters. I'm not sure about the interaction between children and parents in a house where both parents live together, but from my experience, it wasn't just readjustment to Parent A's house (although that was a factor). It was also about the fact that I needed different things from Parent A than I did from Parent B. 

Your caring for your daughters' hearts and minds may be different from the parenting they get from their other parent (and that's okay - we need different things from different people) and that can sometimes contribute to exhaustion. 

But again - I'm just guessing.