If she's acting off then it won't hurt to complete the treatment. It won't hurt anything, and coccidiosis can be very serious or fatal. Correct dosing for the liquid Corid is 2 tsp per gallon of water, make it fresh daily. Treat for 5 to 7 days. Make sure it's the only water available. If...
Corid is very safe and it won't hurt her. Won't hurt any of them. Just no reason to treat if coccidiosis is not the cause. Common symptoms of coccidiosis are lethargy, sitting fluffed up, not eating or drinking well, runny, mucousy or bloody droppings. Chicks and young birds are most at...
That looks like a bit of runny droppings stuck in the fluff to me. I would try to clean them off, if it's cold where you are just use a wet cloth and dry her off completely before going back outside. Possible causes are numerous. If she's acting normally, eating and drinking, running around...
PIctures would help. Corid is used to treat coccidiosis.
Vent gleet is a fungal infection caused by an overgrowth of yeast, treatment would be different for that. Need to determine if it's that or if it's runny droppings built up in the feathers.
How old is the bird? Hen, rooster, how...