I purchase three from Ideal and she is one of those. I lost one to a coon but that's another story and posting. I have three that I bought from a guy in Amsterdam, NY for $10 each and a roo as chicks. I've got one that lays nice dark eggs and all my Cuckoo Marans are excellent layers. I average 4+ a day. Even in this cold weather. I attribute that to my feeding regimen and a light inside to extend the day hours. My marans aren't out much or hardly ever as I don't have a run for them. Yet!
I have 19 others who are let out in a run but don't lay as well. 4 are older Dels (over a year or more) Others are younger (1yr on 2/25) 3Aus, 3SlW,2GlW,2Dom (1 setting), 2BO,7DELs,(3hatchery).
I would check craigs and try to find eggs or chicks there. The hatchery birds aren't as dark feathered nor lay as dark eggs. Hopefully the Roo will help in this area. If she is broody she'll get the darkest of the eggs to sit on if I can work that out. Remember if you have a broody you can switch out eggs for the ones you want early in the game.