My 19 chickens are 10 weeks old. They have been in their coop since 6 weeks. I got them when they were one week. They were in the house in a large brooder for the first 6 weeks. We are in the process of building a predator safe run. I go out to see them and spend time with them in the morning and in the late afternoon and sometimes more often. They have been very happy and calm chickens until tonight. I went out to do the late afternoon cleaning and treats and talking to and petting, etc. and they were all in one corner of the coop frightened. They were all trying to get into the corner. I was able to calm about half of them down by talking calmly and petting them. Some I had to hold for a while but they finally calmed down. But about 7 of them just would not completely calm down and I decided to leave the coop and let them figure it out since all the rest were now up on their roost and bedding down for the night. They were not even interested in their special treats that they always love. The previous night we had a horrible thunderstorm but this morning they were all fine. I want to mention that the coop is completely predator safe. It is a metal shed with hardware cloth venting. The floor is hardware cloth with pavers on top of that. Nothing can get in so I do not think that would be it. I am very concerned. How do you calm chickens down once they get so frightened?