Lethargic, large crop, one eye closed, shivering, hen

I just noticed a hen with one eye closed, just standing around. At first I thought she was sleeping, but when I approached she moved and I noticed one eye closed. From time to time she would open it, then close it back. I picked her up and she was shivering a little and her crop feels really large. I picked up another hen and her crop seems much smaller and lower on her body. The other one won't extend her neck when I sqeeze gently on her crop.
The eye looks okay - no swelling, puss, etc, just closed. Otherwise she looks fine. She's a 9 week old Dominique.

Any idea's?

 

I haven't seen droppings yet. I went back out after posting and she was actually standing in the yard sleeping. I put her in the coop, but she came back out to be with the flock.
Just fyi - I feed them fresh ground organc feed, and they free range. They eat lots of grass, bugs, frogs and occassionally a little sweet corn and tomatoes.

I'll isolate her and see how her doppings look.

 

What type of oil would you use, and would you squirt it down her throat?