It would be good to provide more pictures of the actual chicken, instead of ones off the internet. Look for any mites or lice on her skin under her vent and belly, since mites can make them anemic and pale. Injuries, nutritional deficiencies or Mareks might be possible. It is usually tested for...
In addition I would either stop the additives ro the water, or at least offer plain water. You can also place a small amount of feed plus some water to make it mushy. That is an easy way to give more fluids.
I would just check her crop each morning. Most chickens will adjust their crop occasionally, but if it happens repeatedly, they might have an impacted crop.
Oh, I am sorry for your loss. If you would like to get a necropsy through your state vet to find out what was wrong, you could keep her body cold wrapped innplastic bags in the fridge or on ice in a cooler. Just don’t freeze it. Here is a list of state vets to contact...
Canker is one of the diseases I would cull for in my chickens, since it can affect the whole flock. The state vet lab can do a necropsy and tell you exactly what is wrong. That is a personal choice, but I would at least get a necropsy if she doesn’t recover. If you chose to do one here is the...
Can you post any pictures of the swollen legs and feet? You have to avoid lidocaine and other -caines in poultry. They can be used in small amounts by vets during surgery, but they can be toxic to chickens. Vicks is recommended by the APA to treat scaly leg mites. The menthol soothes the pain...
Was your hen eating chicken feed during her Corid treatment? Or was she not taking food due to her coccidiosis? Let us know if the B complex helps? Have you ever had Mareks disease or any unexpected deaths in your flock before?
Valbazen (albendazole) is no longer available at this time. But you can get the generic albendazole here in smaller less expensive quantities:
https://toltrazurilshop.com/products/albendazole-11-36-liquid-solution/?srsltid=AfmBOooK2wfRQFKX3oRka1hUhFsnzHd748yDIJ-5yHfo4S-2KbIn6tOU
Dosage is 0.08...
Sorry for your loss. What state are you in @bendelstate2 ? Most state vets will do a necropsy if you keep the body cold, not frozen, and take it in or ship it overnight. That would get you a diagnosis. Here is a list of state labs to contact...
Just to see what the wet form of fowl pox looks like inside the beak and throat, here is a graphic picture of it in a hen during a necropsy:
https://tvmdl.tamu.edu/case-studies/diagnostic-guidance-fowl-pox/
You all have a lot of fowl pox down in TX, so that would be a good possibility. Pox is a virus carried by mosquitoes, and lasts around 3 weeks. There is a vaccine available for those not exposed, by she would be immune to it in the future. Here is some reading about it...