I have some older red comet hens..4-5 yrs old. Recently I noticed one was very sluggish and kept slowing down till it was just lying in run. I put it down and noticed yesterday another hen that is same age was inactive. Both hens had bluish/purplish comb compared to red on other hens. The latest hen had swollen crop. When I caught her to separate from flock a large amount of fluid ran out of mouth. Any ideas as to what is going on?