Please HELP me with my sick, lethargic, eyes-closed chicken

I am heartbroken! My 9 month old Rhode Island Red crossbreed started acting weak (not moving much, eyes closed) on Friday ( we had fed hens a random mix of shrimp, noodles, and papaya, not sure if that is pertinent info). We isolated her and just soaked her in Epsom salts because we thought she was egg bound. Saturday, she laid an egg, but further deteriorated...lays down all the time, doesn't eat or drink. Someone gave us Sulmet (which was slightly expired, not sure if that matters) but we have been syringe feeding her Sulmet and water. Sunday, no progress on the Sulmet, and I started to see a clear, sticky mucus in her beak. Now it is Monday, I am getting worried it wasn't cocci, since I have never seen outrightly bloody feces. I switched to an antibiotic (oxytetracycline) and have been trying to syringe feed some sweet potato and mushed up starter feed with water. She is breathing very lightly ( sometimes I have to double check she is still alive), comb is completely bent over, eyes are always closed, head flops over all the time, as if she just doesn't have energy to keep it up, mucus in her beak. I had a feed store guy check and there is no impacted crop, but she does have a wet dog smell to her. Her feces was brown and solid(ish) this morning, but she still has diarrrea which is white and yellow, and white and brown. What could this be?? Viral? Bacterial? Should I continue with Oxytetracycline? Switch back to Sulmet? Both? I am a totally new chicken owner, please help!! I should also mention, we have 3 chickens in our coop and none of others have these same symptoms.

 

We do have a vet, but expensive and not an option. Can I see cocci in feces with a microscope? I could probably see worms, right? She is oozing out of her beak a clear sticky liquid. I suppose I will keep on the antibiotic for a few days ( if she holds on ) and then switch to Corid as a third option...I don't want to give up too soon on the antibiotic if it is indeed bacterial. She has been given medicated starter feed when she was a chick, so is it likely she has cocci? She is puffy and very pointed on the ends like a football. I attached some photos. One of the photos shows a comparison between our healthy chicken and our sick gal, in addition to a shot of her feces (the container she is in is red, that is not blood). Thank you for any help!