3 Buff Orpingtons have dies in 6 months

[meltrav]

We are new to raising chickens and we have had 3 Buffs die in the past 6 months. They always have access to fresh water, feed and have more then enough room in the coop and the run. They have some outside space to roam (not a lot, but enough to scratch and get bugs). We have intorduced 6 new Barred Rocks in the spring but there have been no conflicts betweenthem and they act as one flock.
No signs of illness, or disease. They have been fine one day and dead the next.
Is this normal? Do Buffs have a short life span or am I doing something worng?
Thanks!
~Melanie

 

[sourland]

How old are your buff orpingtons?

 

[meltrav]

Sorry, I forgot to add that. We got them last spring so they are about 15 months old.