She might have hurt herself jumping from the roost. Some injuries will improve on their own given some rest.
Do you have a heavy rooster?
I once had an Araucana hen that a few times really scared me, laying spraddled and not able to get up on her own. After picking her up her up and relocating her legs, she ran and went about her usual chicken stuff as if nothing had happened. I found out that it was the (too heavy for her) Marans rooster that caused it, but she loved him and would not tolerate to be separated from him.
It happened only a few times right after mating, so I left her in his flock and she lived to be 6,5 years.