My first flock of chickens just started laying about 2-3 weeks ago. The past couple of days I've notice two hens eggs have very hard, small bumps on the surface mostly in the more rounded end. What is causing this? One of the eggs is coming from my EE who had been giving me lovely, smooth green eggs but now they've got these had bumps on them! Is it the cold, some deficiency? Any ideas? Thank you!