sad to hear that- chickens can be a bugger to put right- and we always try to put it right and attend to the basics like worming, watching out for them getting egg bound etc. Last year we managed to lose 4 for no obvious reason other than they died on us. this year all are present, correct and fighting fit and not lost one since last Christmas morning- i'm sure there's more to it but sometimes it just seems that chickens die regardless of what we do and sometime they don't