Here's my response:
|A young bird of a different color. See comment attached to |
this blog for information on pied colors, different than this one.
It's unlikely the dark color on your hens is caused by a deficiency, but all birds can show feather damage if they suffer an illness or go through a period of time where they receive inadequate food. Starving birds don't produce healthy feathers. I discussed stress bars on feathers in an earlier article. Here's a link to it.
|After losing feathers damaged by mineral oil, they grew back|
in dark. This is Sugar about a year ago.
|This is Sugar after molting off the darker feathers.|
They came back in as they were before being damaged
and then regrowing in darker.
These are before and after photos of Sugar, who suffered egg binding and survived.
Currently, she's on eggs again without any problems. Trust me ... this REALLY IS the same bird.