1 chicken dead and another unable to walk

[MarissaGayle]

I went out to get the eggs this morning and immediately noticed that one of my buff Orpingtons wasn't acting right. she was laying in the corner of the run and unable to walk. When I opened the coop, I found my other orpington dead. Both of these chickens seemed fine yesterday and the rest of my chickens seem fine as well. I checked both of the orpingtons and there's no blood, no broken bones or any other signs of injury or sickness. I felt around the vent/underside of the Orpington who is still alive and she isn't eggbound. She is missing some feathers around her belly but other than that I can't find anything physically wrong with her. She still wants to eat, but she won't drink and is unable to walk. I'm at a loss as to what would cause this and I'm worried that I might lose all of my chickens. Does anyone know what this may be? And how I can prevent it from happening to the rest of my chickens?
Edit: I'm not sure if this is just a coincidence or not, but these 2 chickens are my only orpingtons. The unaffected chickens are all different breeds. They're 2 years old.

 

[0wen]

What does their poop look like? If you rub/pinch their feet do they move them? What does her crop look and feel like? Any abnormal odors coming from beak or vent?

 

[King CreekRanch]

Can you post a picture of the hen that can't walk?

 

[MarissaGayle]

What does their poop look like?  If you rub/pinch their feet do they move them?  What does her crop look and feel like?  Any abnormal odors coming from beak or vent?

the orpingtons poop is white and watery, the rest of the chickens poop is normal. She moves her feet when I touch them. Her crop feels normal as far as I can tell, she looks normal overall besides not being able to walk. There's no odd smell either.

 

[MarissaGayle]

Can you post a picture of the hen that can't walk?

She can stand up about halfway in a somewhat hunched position, but when she tries to walk she loses balance and falls back down.

 

[MarissaGayle]

She is still cooing and making all the normal chicken sounds, her eyes are bright and alert. Everything about her seems 100% normal except that she can't walk and the watery white poop. I'm at a complete loss as to what could be wrong.

 

[MarissaGayle]

Here you can see her trying to stand but she just falls right back down.

 

[MarissaGayle]

Her appetite is normal as well but she won't drink any water

 

[0wen]

When was the last time she layed? You could syringe her some water. Is her comb pale?

 

[MarissaGayle]

When was the last time she layed? You could syringe her some water. Is her comb pale?

I'm not sure when she layed last but ive been getting the same amount of eggs as usual so I assume within the last day or so. Her comb is bright red.