Where my chickens live, it almost certainly means worms.
I had one last week passing pure water and had a fever, and another a few weeks ago that was passing water all day. They both proved positive for worms and after an overnight worm treatment they improved. I forgot to retreat after 7 days, and they both had fresh outbreaks because my medicine doesn't treat worm eggs.
An adult hen can handle worms better than a juvenile, that's why she seems to be normal. If it was a chick or juvenile, you would see loss of appetite and other problems like pox outbreaks. That is my experience.