Throat issues?

[Chickens_321]

So I have a few chickens that are going into their 10th week now but I’m extremely concerned about their health. Sometimes I’ll catch them doing what seems like gagging but I’m not sure if that’s exactly what it is or if it’s at all normal. They started when they were younger but then it stopped for a few weeks so although I was concerned I thought whatever it was went away however one of my chicks has recently started doing it again and my concern has grown. I have a small snippet of the chicken doing it so if anyone could tell me how to show it (the video) so people can get a better idea of the possible problem I would appreciate it.

 

[Wyorp Rock]

For video, upload to YouTube and provide a link.

It sounds like they are adjusting their crop.
What do you feed and do you provide a source of grit (crushed granite)?