You can't be serious...are you?
A layer type feed has the proper amount of calcium.
I am 100% sure that if you are feeding your birds the way you mention in this thread they are not getting a complete balanced diet.
I am 200% sure that not getting a balanced diet leads to death much sooner...
Chickens are usually asymptomatic carriers.
Next time you lose a bird you should really get a necropsy done by your state lab.