4-5 week old chick falling over

[Antonia F]

I have a chicken question if you have the time to give me pointers. Of the 6 peeps I started 5 are progressing nicely. They are all approx. 4-5 weeks old. I found Phyllis 5 days ago on her side in the coop not looking very happy. We had just installed a roost. I brought her in and made her comfy. No signs of trauma. She eats. drinks and is growing but is unsteady on her feet and we have to set her back up. She seems weak on her right leg and usually falls to that side. Poops, eyes, wings etc are good. She holds her head erect and not to one side, I even thought of an ear infection. I have been noticing her crop sets to her right side and has been rock hard. I compared it to her sisters and they are all softer. I massaged her crop this morning and apparently expressed some of it out as it is now soft. I was hopping that would help her, but not. This morning when cleaning her cage I only lined it with newspaper, no chips. When I let her out of her cage to walk around she follows me, sometimes running and rarely falls over. I suspect she hurt her leg in some fashion in the coop but would have thought she would have shown improvement by now. I feed them Purina start and grow medicated.