Hatching marans

My total experience with hatching marans is very limited but here it is. A friend brought six large beautiful dark marans' eggs. They weren't shipped. They were driven. None hatched but the Easter Egger eggs put in the incubator as a test hatched. None of the marans' eggs even started developing at all.
Meanwhile last spring I purchased several marans hoping to use them to get olive eggers. They are eight months old and only one is laying, and not well. She started at six months and in the next month laid two or three eggs a week until she laid twelve (a clutch?) and then quit.
My hens of other breeds the same age are laying. Not sure if it is because we are going into the coldest weather and shortest daylight hours or what. Most of my chickens lay early and often. At this point I'm not sure if I want to use them in the olive egger program or I will just be bringing the number of eggs produced by my hens down. My Easter eggers are all excellent layers. One I hatched June 6, started laying at 5.5 months and hasn't missed a day. She came from a test egg I threw in the incubator with some shipped eggs and those hens are now 6 months one week old and none have laid, although one's comb is reddening up. .So I'm hoping.

 

I have read that too, due to heavy coating and candling difficulty.
I would ask about it on the Marans thread in the breeds forum