I was GIVEN a hen as a rescue (from someone who had two hens, one died, the other was lonely, and the head of the household wanted to get rid of her because she stopped laying). They thought she was a RIR and named her "Red."
I was shocked at her condition. They also gave me all the feed left... it was scratch! They were only feeding her scratch! And orange slices... My friend who transported the hen 500 miles to my house told me the coop was filthy.
Well, her comb and wattles were really pale and she had scaley leg mites SO bad her legs and feet looked like those of someone suffering from advanced Rheumatoid Arthritis (far worse than what I see in the photo of your rescued hen). Plus, she was a Gold Laced Wyandotte.
I quarantined her, treated her, and put her on regular, all-purpose "All Flock" feed. The former owner - I was gentle when e-mailing her updates, because SHE liked the hen - didn't even know what scaley leg mites were and was mortified. Then I emailed her a photo of how she looks now.
That's George, one of my Silver Sebright roos, with her. The caption to this photo would be: "Get BACK! She's big, she's beautiful, and she's MINE!"
So I am sure your rescue hen is happy and will be healthy before too long with the proper care.