Strange scale top of foot, chicken limping

[AdrianBlue]

I have a 2 year old copper Maran hen who has this strange scale on her foot. It is the only difference between her two feet, and it is definitely causing her discomfort. She's limping/high stepping on that foot. She lays down a lot, especially in comparison with the others. She roosts on a 2" x 4" which lays flat on a bracket and is cleaned regularly. The floor is dirt and rock, and the nesting boxes have fir shavings. There are 6 other hens, all seem perfectly fine, none of the others have a scale like that. The skin under that scale looks good, not inflamed or injured.
I have soaked her foot in Epsom salt and neem oil for about 12 minutes, scrubbed with soft toothbrush, rinsed and dried her, and put mineral oil on, wiped it off, then applied vaseline, just in case she had scaley leg mites, and it didn't seem like it could hurt.
Has anyone else seen anything like this? Any suggestions for treatment?

 

[Aunt Angus]

I've not seen anything like this. She's feather-legged, right? I wonder if it's a follicle cyst under her scale??? Maybe???