What was the cause of the death?

[chicken12344]

I came outside today and found one of my hens dead. They are free range and about 3 years old. I don't remember the breed. About a week ago was puffed up and not moving much and her waste was a liquidly green. After a while she got better and was even going on the roost with the other hens. However today she came out of the coop and was acting like she was a week ago however she was not moving as much and her tail was moving up and down and she was kind of bobbing up and down. When I threw in a treat for them she was interested and went after it. Not even three hours later she was dead. This really sucks because I just lost another hen yesterday to an impacted egg.
Could it possibly be an impacted egg or something she ate? None of the other hens are acting strangely.

Thank you

 

[nuthatched]

I'm sorry you're losing hens. What do you feed, including treats? Could they get into anything they shouldn't?

 

[chicken12344]

I'm sorry you're losing hens. What do you feed, including treats? Could they get into anything they shouldn't?

We feed them this:
Link
I am not sure why its that much on that website.

For treats, (which we don't give that often) we will give them table scraps.

I can't think of anything they could get into. We do have a compost pile but, there's usually not that much in it except dirty shavings from when I clean the coop.