The pictures of the feet above look like a much more serious version of what my hen's feet look like. Her swelling in her feet has gone down again today to where they are barely even swollen anymore. Her abdomen remains swollen, though. 
 
While examining her today I was trying to see the skin around her abdomen (which was slightly darker than usual), and there was some sort of parasite. It was yellow, very small, and very quick. She has had no loss of feathers. I've never had any problem with parasites in all the 6 years of owning chickens. Wild birds cannot get in the run, any added chickens are always checked and quarantined (and no new birds have been added in a year), and I examine my chickens for parasites. Mice can get into the coop, since they are a big problem where we live. Is it the parasites that might be doing this to her? This is the first sign of anything on my chickens EVER, and she does not have scaly legs. Also, are these creatures, whatever they may be, transferable to humans and our house? She is inside right now as I try to help her, and we really don't want whatever it is to infest us and our house. 
 
We have some DE, but it is rated for insects and not food grade. I'm hesitant to use it until I know if I can.