Dirty vent, squishy crop, weak. What's wrong? pics!

[lillyrosesmum]

I noticed yesterday that one if my hens was laying down a lot more than usual. Today she was worse. She is still eating and drinking some. She is dirty around her vent and her crop feels like a water balloon. She has been losing her feathers so I guessed she was molting since it's about time because she is about a year and a half old. I checked her for live and mites but u don't see anything. What should I do for her?
Her vent

Her missing feathers

Her comb

 

[lillyrosesmum]

Oh and she had gradually started laying less and less which I attributed to molting. Her last egg was about a week ago and the shell was so thin it broke in the nesting box. That's her only thin shelled egg ever.