one of my chickens has this swollen foot. It looks like a cyst. It's doubled in size in a week or so. and she has been getting picked on really bad by the bossy chicken. not sure if this is because of her foot and she is weakened? the others seem to leave her alone but one chicken has almost killed her and is now in solitary confinement.
this is also a white leghorn but some of her feathers are turning grey...I tried washing her thinking it was dirt/mud...but does not seem to clean off. the other leghorn is still nice and white.
the bird is about 15 months old.