Strange sudden problem, not sure if it's an injury or illness or what

Sorry for the long post, but I don't know if these symptoms are related, or a weird coincidence.

I have 7 chickens that are normally confined to a run when we aren't home and let out to free range every weekday evening and all day on the weekends. Yesterday my husband let them out around 5 pm and didn't notice anything wrong with our Buff Orpington (he can't swear she was ok - he didn't pay particular attention to her - but there was nothing wrong enough that it stood out to him) around 7, I walked outside and called "Chickens!" which usually bring them all running for treats, and Buffy (the buff orpington) is usually at the front of the pack.

Well, she didn't come, and we started looking for her. We finally found her under the deck. She was just standing still, with her wings out slightly from her sides, her head and tail down. She had just laid an egg and was standing over it, but she didn't cluck or anything (they usually make a huge racket right after they lay - they also always lay in their boxes.. even if they're free ranging, they'll go into the coop to lay, so her doing it under the deck was unusual) I went under the deck to retrieve the egg, took it right from under her and talked in a soothing voice to her and she just looked at me. I decided to leave her alone because I didn't want to stress her out.

A little while later my husband coaxed her out from under the deck by putting a waterer out, and some scratch. She drank, but didn't eat the scratch, which is unheard of, and she was walking really slowly with head and tail down. He noticed that she had a pretty nasty cut on her comb, right by her nostril, where the comb joins the beak. It had some semi-dried blood on it, didn't look fresh or particularly old. So we figured that was why she wasn't eating - her beak hurt. It was starting to get dark at that point and the chickens were all heading into the coop, but my husband was still worried about Buffy not eating, so he brought her a mealworm (their favorite treat) and she looked at it and when she moved her head to take it, she vomited.

I searched this forum for posts on chickens vomiting, and most of my hits were on sour/ impacted crop. We caught her this morning and I felt her whole front, from her neck down to her breastbone, and I didn't feel anything like a hard or distended crop. I grabbed one of the other chickens and felt her to compare. Buffy felt fleshier, but I couldn't feel any noticable lumps. However, she was still very listless and drinking a lot but not eating. Also, when she drinks, it looks like half the water runs back out of her mouth, and she had a greenish gray patch of something on her feathers below her beak this morning.

I have no idea what could be wrong with her. If it's a crop problem, I obviously don't know what I'm looking for, and the injury makes me think it's related to that.. None of the chickens has ever been sick or injured before and it just seems like too much of a coincidence that one would hurt itself and also happen to get sick at the same exact time.

Any suggestions?