I am having this same exact problem with one of my Black Java hens and I am dumbfounded....completely at a loss. She is my best hen and just the age to begin laying. Nine days ago I fed her and there was no issues that I noted, she ate well but the next day, just 8 short days ago I checked on them and immediately noticed her laying on the ground with her wings spread out from her body; I was so worried I brought her inside my home immediately into the incubation area where I placed her in her own section and have been monitoring daily (several times daily, in fact). She continues to eat and poop regularly, she is just extremely listless, almost lethargic, moves very little but when she does her breathing becomes extremely labored until she is gasping for air through her opened beak. Yesterday morning,she stood for the first time in a week- it only lasted for a few seconds and then she was laboring to breathe again!, It is absolutely heartbreaking for me- I have no idea if she is in pain but I have given her antibiotics for @3 days and today I added the Apple Cider Vinegar to her water. She drank it with no problem. There is no discharge from any part of her body, poop is still regular and consistency is fine, comb and skin are normal. I am lost; What can I do? Thank you!