I'm one of them that dont handle animal deaths very well. However, because I do take good care of my animal family and will pay what's needed at a vet, it does help to relieve the pain, knowing I did give them a good life and did all I could for them.Failure to thrive is most likely what happened. I think more than likely a genetic mistake.
I have found that kids follow your lead, so how you handle it they will follow.
We are of the group, dang it... circle of life, not so much of the guilt, I did something wrong. I do sometimes think chickens are not for people with great sensibility as chickens do die rather easily, and generally do not live for years.
One of the reasons too I'm buying from a breeder within pick up range rather then shipping and buying from a hatchery. I will know they had a good start.