Sick hen?

[Nene_putnam]

I have a hen that I’ve noticed what seems like a cough or sneeze... she recently stopped roosting at night and just lays on the bottom of the hen box. She was a new layer but never payed in the hen box and always ate her egg (I assume it was her eating it) but now she has stopped laying which so have a few of my others. I need to keeping chickens. I got them in April at 2 weeks old. She eats, drinks, and mingles with the other like normal

 

[Wyorp Rock]

Can you get a video of her? Upload to youtube and provide a link.
If no video, some photos please - pullet, her poop, etc.

Were her eggs normal (hard shell, no defects) or was she having production difficulties (soft shell, shell-less, etc.)?
What do you feed, including treats?
How much ventilation in your coop?
How much roosting space is in your coop?
Coughing and sneezing, if often, could be due to respiratory illness. Do you notice any mucous from the nostrils, watery eyes, etc.? Have you added any new birds recently?

Check to make sure her crop is emptying overnight, look her over for lice/mites. While checking her over, feel her abdomen below the vent between her legs for bloat or fluid.

Hard to know which direction to go since she's eating/drinking and mingling - doesn't sound like the coughing/sneezing is prohibiting her from any of those activities, so observing her to see if she gets better/worse may be the course of action to take. An antibiotic may be necessary to treat symptoms if they worsen.