I've searched the forum and didn't find this exact problem, if it is indeed a problem. I have a Black Copper Marans hen that has alway had a dark spot in her eggs. She about 3 - 4 years old. It's a nice large egg too. Just want to make sure it's ok and that she won't get super ill or anything.
There's a good article regarding egg abnormalities that may be of interest to you. Here's a link to it: https://www.backyardchickens.com/a/common-egg-quality-problems If you scroll about 1/2 way down, blood spots in the egg are addressed. Hope that helps.
