Ummm, welll if you are just locking down- well, no, because a few .1 or .2 degrees won't hurt the chick, make sure their is plenty of moisture in the incubator so chicks don't stick to the shell.
I highly doubt that was because of you, it sounds that one is highly disformed- don't buy Maran eggs from that place again. I think it is genetics, but how many eggs total did you hatch with flock eggs?
the black copper marans can be very discouraging. I have always been able to hatch chicks. the marans can just quit on you. I kept thinking I was doing some wrong. I got 2 dozen more eggs from my friend only moved them 3 miles only 6 hatched. probably 12 didn't get out of the shell. the other 6 un fertile. She even has a hard time hatching them... WISH people that hatch them successfully would release secrets (LOL) Plus they seem to died very easy after hatch.I got discouraged a sold my flock off. Just to start over got the 2 dozen eggs. I think there is 5 chicks out there. When a beautiful young roo desided to eat plastic netting and choked to death. Not only are they hard to hatch thy're stupid too. LOL.
Plus I have seen the same thing happen under broodys. (not getting out of shell) it is a marans thing. or just LAZY chicks....