PaisyQ, you might want to keep the flocks separate for a while to make sure it was just a random death - I would suggest 2 weeks. And I agree, sometimes chickens just die, and it is hard sometimes without expert help - or even with it - to know exactly why. If your birds seem healthy, eat well and are active, then you likely have nothing to worry about.
Amber links are sex links, you should have received just pullets.
Amber links are sex links, you should have received just pullets.