I know this sounds really strange to ask, but one of our 7m old BA's ( Black Austrolorps) laid an egg that had a good sized black spot on it 4 days ago. I didnt think much of it, and put it in the fridge with the other eggs. This morning I went to put the last few days eggs into a carton and when I picked up the egg with the black spot, the spot had eaten into the shell. I picked away the shell to the 'skin' layer and the spot is now on the skin. I was able to pick the spot off of the skin, it almost reminds me of a scab. The egg inside seemed ok , but I threw it out just the same. Does anyone know what this is? She hasn't laid another one like it since Thursday.