Suddenly sick chicken

[Andreab]

I have a hen that is my daughters favorite. We went out this morning around 9:30 to feed and she was acting normal and came over to eat. This afternoon around 1:00 we went out to let them outside. The hen was breathing with a high pitch noise and sneezing. She looks fine and has clear eyes and no mucas. She is trying to eat some grass. Does anyone have any suggestions I am not sure where to start. Thanks for any help.