Seems very possible, you may have stumbled on to something. A lethal white gene in d'uccles and - araucanas lethal in general. Very interestingWhat's weird, beside that beautiful choc mottle coming out perfectly d'uccle, is that my extra pale chicks die. As in a lethal white gene. Not sure if that is what it is in chicks, but I know horses have a lethal white gene. All the chicks in the first month. Not the others, just these pale babies. Maybe if momma raises them, the chicks can get any antibodies from her.
Any ideas anybody? Ever hear of a lethal gene in chickens?