I have a large flock of different ages of chicken in the same cook (in different pens) but I have four rhode island red hens that are 4 years old, for the last 1ish months one of them has been getting skinny and would not try to walk away from me like the rest when i came near, she was slow and didnt lay many eggs, almost none! then here comb became droopy and pale, and today i found here dead under the roost, 2-3 months before 2 of my welsummers died and where in the same position under the roost dead, all different ages, but with the welsummers they seemed 100% healthy and fine, then in 3 days, they both died