New chicken owner. Have 5 white legs raised from chicks with 8 Red Stars. 24 week old white leghorn; just noticed blood on chest 3 days ago and pale comb. Picked her up this AM and noticed large patch of bare skin overlying chest with a furuncle in center of patch slightly scabbed over. Seems to be eating & drinking ok. Not sure what poop looks like, but the roost pole in coop looked like it had some old blood on it. Not sure if from chest wound or poop. Last week I added a splash of bleach to water bucket to disinfect nipple waterer system which I've done before. None of other 12 chickens having any noticeable problems. I have some permethrin dust/powder if needed. Any suggestions would be greatly appreciated. Thank you.