It must still be cold in Michigan, especially at night! The queen won't lay any more eggs than the number of nurse bees can keep warm enough to survive. Finman has a trick that I'm trying this year, which is to put a small 8 watt terratrium heater on the bottom board just to give them a boost of warmth to give the brood a fighting chance on those cold nights. Try this, and maybe some pollen substitute, and see how it works out! :D