One of our 1 year old Buff Orpingtons has suddenly become quite lethargic. She is standing up like normal, but not walking much and she sits down immediately if we pick her up and put her on our laps. Several hours ago when we got back from work she was fine and acting normal. As far as I know, she has been laying as normal. She is eating well when presented with food, and has pooped normally since we noticed she was acting strange. She is preening and acting completely normal- except for being unusually calm. It's like she hit her head on something. She also hasn't made any noises, though she is usually vocal when we are around. Vent looks normal, and she seems to have no problem flying when jumping down from a height. We are currently keeping her inside until she recovers or otherwise, and are about to run to the farm store to get some antibiotics and electrolytes. Any ideas or suggestions would be appreciated!