I was going to add that your bp should be on adult mice by now and probably isn't pooping due to the lack of food size with a growing youngster. Also could your bp possibly be near another shed? I've noticed that my girl will hold it until shed and then unleash hell. As she is doing right now. I know either tomorrow or th next day I'm in for a lovely clean up. And its off topic but buy a food scale that way you can weigh your bp and feed around 15% of the body weight. Also its good to know the growth rate or if they lose too much weight in future hunger strikes. Also I would keep your humidity at 55-60% and 70% during shed. Good luck.
By the way don't forget to post a pic. Always love to see the bps!