Sounds like we have the same problem. I posted this in the Arizona forum
"HELP!
Checked the girls this a.m. and my Polish seems to be having trouble walking. She's not squatting or bowing but just sitting on the ground and when she moves it seems like she's crawling. She hasn't laid an egg in a few days, nothing unusual, but she seems distressed. The other girls are just fine and my makeshift swamp cooler is keeping the temp in the coop cool enough that they don't pant, although she is now. I examined her but found no wounds, bleeding or anything else, she didn't squawk when I picked her up, like if I touched a sore spot.
Could she be egg bound?
Is there something I can check for?
I'd hate to lose her, she's a beauty. Any ideas?"
It's been really hot here and it could be heat for you too. The answer I got was...
Now, my guess would the heat. Bring her inside if you can, and put her in a cool, but not cold, bath. Regular tap water temperature is probably fine. Also, make sure to give her water with electrolytes in it, like Pediasure. As she professes some, try a softer food like scrambled eggs or raw yogurt. Both are excellent.