wobbly, lethargic hen - what can I do?

Hi,
This afternoon I went to let the chickens out to range and Iris didn't feel like leaving the run - *very* unusual. Here are her stats:

1) What type of bird , age and weight. -- Barred Rock, 10 months old or so, not sure of weight (sorry!)

2) What is the behavior, exactly. -- she seems to wobble when walking - just stands still or sits down, seems to have somewhat labored breathing, no runny nose or eyes, comb looks fine. Has some loose stool stuck to her tail feathers, but vent looks clean. She is eating and drinking still, but doing it sitting down. Also she is fluffing up her tail feathers.
3) How long has the bird been exhibiting symptoms? 7 or 8 hours or so?

4) Is there any bleeding, injury, broken bones or other sign of trauma. -- No
5) What happened, if anything that you know of, that may have caused the situation. -- worried that she ate some foam insulation I had temporarily propped against vents of coop.
6) What has the bird been eating and drinking, if at all. -- yes - interested in some strawberries and hard boiled egg, as well as usual grain and water

7) How does the poop look? Normal? Bloody? Runny? etc. - it looks a little runny, not as much as usual - greenish

8) What has been the treatment you have administered so far? -- I've separated her and put her in the garage in a big tub with a towel, heating pad under tub, heat lamp, and food and water. I'm thinking of giving her a partial bath tomorrow am just to clean off her tail feathers.
9 ) What is your intent as far as treatment? For example, do you want to treat completely yourself, or do you need help in stabilizing the bird til you can get to a vet? I'd rather take care of her myself.
10) If you have a picture of the wound or condition, please post it. It may help.
11) Describe the housing/bedding in use -- pine shavings in coop. straw and dirt in run (the straw I put down on top of the snow. But now the snow has melted, so it's a little muddy.)

Our other four hens are fine so far - and I'm not sure which ones started pecking that foam insulation - but I've removed it.

These are my first chickens, so I'm not sure even where to feel for her crop to see if it's impacted. I rub her breast area but don't feel anything hard. And I checked my other chickens and everyone's breast area felt the same. If that's even where I should be checking. And she doesn't seem to care for my checking (I read that chickens enjoy a crop massage?).

Any ideas would be really appreciated - I'm sure we won't sleep well tonight for worrying!
Thanks!

 

Thanks, Chookchick.
Woke up this morning and she was panting with her beak closed (she'd been panting with it open last night - started after I posted). I picked her up to change her towel - it had a few spots of poop, but nothing big. Crop felt the same to me. When I put her back down on the towel, she closed her eyes and started flopping her wings, stretching her neck, and then she died. So sad! My kids are going to be even sadder. I'm wondering if it's something I did when I moved her. I can't be sure, but she'd laid an egg at least two days ago, maybe not yesterday. I couldn't feel anything egg-shaped-like when I felt her abdomen, but I've never felt the chickens that closely before - now I'll be sure to do it more often. I'm just crossing my fingers that when it's light enough to get out to the coop it was nothing contagious.