2 Buff Cochins Dead, 2 more Crated, what is going on?!

We had 5 Buff Cochins and are now down to 3, with two of those currently confined in a large dog crate in the basement. I posted a few days ago about having to put down the first one due to severe picking after, what we have now learned, was a prolapsed vent. THe second one then seemed to prolapse (posted pics the other day) and got picked but not as bad as the first since we caught it sooner, but she still died yesterday in the crate. THEN we went out to do the evening chores (despite the snow the chickens had mostly been free ranging yesterday) and found 2 more Buff cochins with their rear ends very swollen, and one was being pecked by the other chickens. Those two are now in the crate inside to try to prevent what happened to the other 2. 1 more is left with the flock and, as of this morning, looked completely fine.

How could they all have had a prolapsed vent?! Is this something Buff cochins are prone to? None of the other breeds we have are showing signs of this (feathers being picked out or swollen rear ends). Are we doing something wrong?! I am also concerned this is starting a very bad habit amongst the flock of pecking others to death.

THanks for any advice.

 

THanks for the replies No, the ducks and chickens are housed separately. When we are home, they all freerange around our property, but do not seem to mingle (don't like each other). But you are right, I am concerned that the cannibalism is becoming a nasty habit.

I will definitely look into a vitamin D deficiency, that is a new one I had not thought of or heard of.

Today went well for all involved. no new pecking on any of the remaining free chickens. The 2 in the crate are very lively and seem to be doing ok. I put preperation H on both tonight and cleaned them up as well before hand. Both very swollen still right near/under their vents.