loud breathing with mouth open and sneezing on 7 month old hen

[Henriettasdad]

We have a hen that is one of 9 that developed cold-like symptoms recently. Her behavior, appetite, weight has not really changed. She has been laying for a couple months. Weather has been wet here in FL lately. I was wondering if she needs any treatment or if this is not a serious condition. All the hens get a lot of free range time and handling from the kids.