Lethargic droopy tail

[Notebook]

I have a hen who I thought was nesting under the grass outside, but upon further investigation I discovered she was just listless, standing or sitting there in the shade staring at me, or with her little eyes closed. Her tail is sagging downward too, and she looks like she doesn't want to move. She laid an egg either last night or today, Im at a loss and Im starting to get worried. Shes always been a quiet chicken, but not this quiet.

Does anyone have any idea what could be wrong or what I should do?