To address a couple of your other concerns - The black spots on her comb look like peck marks to me. The white-ish patch that you see, imho, is where her comb flops over - my W. Leghorn has a similar whit-ish patch where her comb folds over, take a look at your other girls, I suspect you will find a similar patch if they have the folded over combs like this one. The ear, looks like her normal coloring to me as well.
Crop issues can be a symptom of an underlying condition like worms, Coccidiosis, infection and reproductive disorders. If there is any way to get a fecal sample tested that would be a good idea.
I agree with
@casportpony the poop is concerning. I'm not sure what course of action that she was going to suggest, hopefully she has been in contact with you through pm, but I would be inclined to at least start to treat with Corid for Coccidiosis. It could be that she has infection and needs antibiotics, but which one it's hard to know. Since she is hanging in there, the Corid is mild and won't hurt.
Also, maybe I missed it, but you haven't mentioned when she last laid an egg. If she is like mine, she's a prolific egg layer, so she may be have a reproductive problem as well, or has not laid due to other things going on.
Getting the crop to empty/function is important, you may find this article very helpful on that
http://www.backyardchickens.com/a/impacted-slow-and-sour-crops-prevention-and-treatments
Thanks so much, I will certainly check out that link. I will also check the other girls for that big white patch at the base of her comb...she does have little ...patches? of white stuff on her comb and that was what concerned me first, then I saw that big one. I will try to make a pic that I can draw arrows on & that way I can pinpoint things.
I'm just going thru and reading everyone's responses, then I'll do a quick update, then get back to trying different stuff, she is better today tho!
Keep her drinking and see how it goes. Please keep us posted.