She's adopted, no idea of her age, but not young.
She laid last summer through fall, but none of my girls other than the yearlings lay much through the winter, although they are starting up again. I do not believe she is laying yet.
No mucous or other drainage, eyes look fine, no swelling. She does seem to sneeze when eating.
The gasping is mild, it has to be pretty quiet for me to hear it. She gets around the same as always, eats, haven't seen her drinking, but I rarely notice any of them drinking. The coop is fairly tight at night, but they are in a run or free range all day. No mold or ammonia odor that I can detect.
I think I palpated her crop this afternoon (couldn't get to her before she ate). She had a walnut sized, very soft (like mashed potatoes) mass. I massaged it for a while then let her go.
She has lost weight. I didn't notice it until I handled her today.
No other birds have any of the symptoms you asked about.