They eat layer feed, I also have a dish of oyster shell for them to eat as they need to. I also provide them with scratch grains and they free range all day long. I also started putting a little vinegar in their water. I find it strange because it just seems to be one hen that is doing this, out of 30. I don't think its a nutritional issue or the others would also do the same, I would think. We did have a visit from a hawk this past week and it killed two of my chickens but she was doing this before that happened. Respiratory issues? I don't know about that. I don't think so as they all seem very happy and healthy.
Thanks for all the replies! I appreciate it.