Looking forward to what you find out. I am getting Birchen and Blue CM eggs this spring. I have never had much luck with Marans eggs, even when I picked the up.
I have trouble with marans too and I have my own. From 3 different lines. I think fcbms have egg issues because of the egg color selection. Plus they come from limited stock in the us. I know some people have no issues at all but I can get high 90% for silkies but never for marans.
I expect to see the same issues pop up in a lot of the news import lines that descend for 5-10 chickens.
How are you all? I'm hoping it gets to be less of a muddy mess this week.