Well, regardless of the origin of this problem, will have to cull this chick. I just hate to do it. I am going to double check my temp to see what my incubator is running. I think it is right on, but maybe not. I don't want to be the cause of this happening again.
I do have four other basques. They are between 3 and 4 weeks old and getting big. The biggest is 10 ounces! We weighed them tonight, just for fun.
Yes, it is sad to have to cull them.
Humidity can cause hatching problems too. Did they hatch on time? If so, the temps were ok.
Basque chicks are stout and grow very fast.