Chicken with respiratory distress

My 3 year old black Australorp hen has been having trouble breathing (she holds her beak open and pants) and she sneezes a lot, sometimes very loudly. Sometimes she shakes her head, but not very often. She is lighter than the other 2 hens. Currently she weighs 4.6 lbs. She used to be slightly heavier, but she has been light every since about December of last year. Her abdomen doesn't feel bloated to me. She also has been laying eggs regularly for a couple weeks. I cracked her eggs and took a look inside, I didn't find anything irregular. She had not been laying eggs for about 4 months, but started laying again on 3/28/2024 (for 11 days). She started showing symptoms on 3/1/2024 – it has been about a month now. My other 2 hens have not shown any symptoms yet. There is no signs of trauma, such as bleeding, injury, broken bones or anything like that. I am not sure what may have caused her respiratory distress, although I do recall that the hens may have eaten around a patch of fungus before she got the issue. She has had other problems in the past – bumblefoot (which never got that bad and has since gone away) and she laid a malformed egg when she was about 2 years old. Where we live the summers get very hot (100 degrees) but right now the temperatures are in the 70-80s, so I don’t think that heat stress could have anything to do with it. She has been eating and drinking normally. She eats primarily a complete feed (Purina Layena layer pellets) and water. I hardly ever give my birds treats. When I do give treats, I feed them apple, or yogurt with garlic and ginger. I believe that her poop is normal – it is not bloody or runny. Please see pics below. I have not really been treating her with antibiotics or anything as I do not know what disease she exactly has. In addition, I am not a very experienced person when it comes to handling poultry diseases, so I did not want to give her a medication without asking for other people’s opinions on what disease she has and what medication to give. I do not have access to a nearby veterinarian so I am not able to take her to a vet for help. Other chicken keepers have said that I can try giving her Tylosin (used for respiratory illness caused by mycoplasma) or I can try to deworm her with Safeguard dewormer. Although I have already gotten replies from other people, I am making this post because I would like other opinions as well. Thank you.

Hello - and thank you for this thought-provoking question.  Thank you also for not throwing antibiotics randomly into your chicken's feed.  This is a deplorable practise as it can stop antibiotics from working for animals and people across the globe, by allowing strains to develop that are resistant to them.  I can talk more about this if you want me to - and there are probably articles to be found on the blog.  For both bacterial diseases and worms, tests should be performed, either on poo or on the chicken itself.  Chicken farmers often have large numbers of birds and sometimes sacrifice early victims of potentially contageous disese, to the pathology lab.  This helps to ensure that they are treating the flock correctly.  Because you only have a few birds and because in this instance the survival of your individual chickens is important, your vet may need to do tests on their live patients, starting with an examination.  I hear that a lot of chicken keepers follow this 'guessing' culture with antibiotics, but remember that it is just a guess, even when the chicken gets better.  A lot of the time they are wrong. It is not from lack of skill; vets, farmers and members of the public alike are ill equipped to guess from the outside of the chicken what thr problem is.  Sometimes they are lucky; sometimes the chicken would have got better anyway; sometimes the chicken doesn't make it.  Often resistance is spread.  It all depends on what is actually causing the problem and for that (and legal, safe antibiotic use where it is apppropriate) you need to liase with your own, specific veterinary surgeon.