Chickens Can't Eat!?

[LittleBoPeep1]

Hello,
My flock looks like they are having are hard time eating. When they eat, they are pretty noisy and it sounds like they're making little sneezing noises. After they take a bite of food, they sometimes crane their neck up and shake it back and forth! Any help would be appreciated. Thank you

 

[Ol Grey Mare]

How old are the birds in question? How long have you been noticing this behavior? Have you recently changed feed? What form (crumble, pellet, etc) are you feeding?

 

[LittleBoPeep1]

Age: 2-4 years old
I've been noticing this behavior for about 2 months, but it hasn't gotten better
I haven't recently changed feed
Feed: crumble

Thank you for your response!