Over the past 2 months I've lost half of my flock, 5 birds. It starts out with loose stools and progresses to liquidy, whitish diarrhea and lethargy. I have not seen any blood in the stools. It has hit one bird at a time and I've isolated the effected bird as soon as I see the symptoms. The birds continue to eat and drink fine, but continue to lose weight and eventually die. I give the sick ones ACV in their water and yogurt along with their normal feed. It seems to hit a new bird about every 2 weeks, and it's only been one at a time. They are 3 years old, and usually confined to a 25x25 pen with a 10x10 coop. The pen is dirt, and we've had periods of heavy rain making it quite damp. I have not seen any evidence of mites, but there are mosquitoes in the nesting boxes that I've tried repelling with granulated garlic under the shavings. Ideas? Could it be that the pen soil is contaminated since they've been in the one area so long? If so, how can I address it? Thanks for any help.