Brian, im sorry I took so long to get back. I couldnt see anything that was wrong with your chicky. She looks fine on the outside, but that fluffing... what you may want to do is treat her for Coccidiosis and worms. You said that you had not wormed her before so she may have worms and/or Coccidiosis (she does have white runny stool which is a sign).
To worm her, take either: Ivermectin sheep drench- 10cc per gallon of water (for about 5 days)
~OR~
Ivermectin Cattle Injection- 5-7 drops (depending on size) on a piece of bread and put down throat (one time!)
To treat for Coccidiosis:
Sulmet- 2tbsp per gallon of water (for about 5 days)
You can mix both in the same gallon of water if you choose to do the Sulmet and sheep drench. This should help and you should see an improvement quickly if she is infected. You also want to treat the rest of your flock with the same dosages listed above as prevention.
Good luck!