hello, unfortunately in the past month we have lost 4 birds. We are not entirely sure why they are dying. It starts with them being lethargic and mopey. By the next day their cones are pale in color or become deep in red color. Out of the 4 hens, we had 2 continue to pick and scratch at their feed but seem to not eat a lot. After reading about the sour crop issues, I am wondering if this could be whats happening to them? They breathe heavy, tilt their heads forward, we can feel the fluid filled pocket in their chest/crop area. We have tried to gently massage the crop, causing the birds to vomit, (some have a clear fluid, some are tinted in color) the birds pass away while vomiting. We are tilting them forward, just as every forum we read tells us too. We are putting Apple Cider vinegar in their water. They aren't free ranging as much as we would like them too, as we have a horrible hawk issue. One of these birds started with the swollen abdomen, from fluid, which we drained, she seemed to be doing better, then the following day, the fluid started building in the chest area and she too vomited and passed. 3 of the hens have had the fluid "leak" from their beaks before vomited and passing away. We feel terrible. PLEASE anything you can do to help us figure out what is happening to our birds would be greatly appreciated!! We are thinking it could be a "sour crop", however what is causing this to happen?? The hens are between the ages of 2 and 4 years. We have seen a decrease in eggs (we have 20 hens and we only receive 6-7 eggs daily at the most). Could it be something feeding them?? We have 2 roosters in the coop, could they be over stressing the hens? Roosters are friendly.