Hello and welcome to BYC!
I am sorry for your loss!
It's hard to say why your hen died as so many things can afflict chickens from worms, bacterial or viral infections, egg binding, wounds, flock aggression, something genetic, etc... Many times a necropsy is needed after death to figure out what happened.
And of course good hygiene and health care along with good diet, exercise, plenty of space and such helps to prevent a lot of diseases.
As for your hen that is bleeding. Has this been going on a long time? This could be several things from too much over breeding from the rooster, she may have prolapse starting from egg binding or some infection at her vent area.
Is she the lowest in the order of birds? Many times the lowest in the pecking order is run off from food and water and the lack of water is sure to cause egg binding from dehydration....the bird's oviduct becomes dry and she can't get the egg out.
If you have any other clues, please let us know!
Keep us posted!
