I'll say a few more things here and I'll leave you to it. You have several cooks in the kitchen, so to speak, experienced people trying to assist. My personal overall management philosophy as I've said several times is not to do fifty things at once to an old bird who is probably on her last legs because it can only add to her stress and won't necessarily prolong her life. It can be completely counterproductive. You know that's the way I manage my flocks and I've had more than one hen who has lived to over 14 years old, many others to 12+ years so there was a time when there was literally an Old Hens' Home & Hospice happening around here. Most are gone now, but others are coming along behind them; who knows if they'll all live that long? Most have zero real health issues by those ages, and if they did, I wouldn't change my mind about the way we've managed them. What I'm saying is that when you tag me to advise you on anything, this is the advice you will always get, consistent advice based on what has worked here for almost 18 years. I can't in good conscience advise anyone else to do differently. I won't advise anyone else to do what I won't do with my own birds. Others may feel differently than I do and you choose whose advice you will follow, entirely up to you.
To address a couple of Eddy's issues, since this was mentioned ostensibly as the reason she's on antibiotics, I think, I've seen breast blisters/callouses in hens in past years, never had one get infected, never picked one open (which can lead to infection). I have treated many crop issues which were common with two of my largest breeds, Orpingtons and Brahmas, but never used any prescription meds for it. Never knew why those two breeds had issues. All my flocks eat the same exact mini layer pellet and always have, but others don't get crop issues like those two breeds did. This current group of Brahmas are bigger eaters than any others I've had, though I don't recall the Orps being so. Crop issues are almost always symptoms of other internal issues, not the main ailment. Crops can fail because the heart is failing, because the bird itself is failing and for no other reason, or it can be from improper feeding methods or other things. You can treat the symptom, but you are not treating the root of the problem and may never know what that is. The crop is usually a barometer for the condition of the chicken. It can simply mean the organs are beginning to shut down/fail, hard to say. That is just a general statement, not necessarily saying your old girl is shutting down. She could be, but I have no way to know that. A chicken can seem like she's doing well, but they are stoic animals and you may not really know how far gone they are until it is really in your face. I see that with hens who die of old age and have zero health issues. It happens quickly, over a 2-3 day period then they're just gone. Best of luck with your hen. Hope she is on the upswing.