I just read
U_Stormcrow
thorough analysis, and one other thing popped into my mind. ESPECIALLY SINCE YOUR BROODIES' ARE NOT AFFECTED. (they do not wander off)
Is it a possibility someone is poisoning your chickens purposely :idunno
Mix breed should have no effect. Your chickens are not dying from a genetic defect. They are dying from an undetermined cause, that is still a mystery. Without testing the dead chickens, everything is a guessing game. I also know you have no access to get chickens tested.:( :hugs .
My only...