This afternoon whilst I was filling water up one of my bantys had a really strange turn. She starting whizzing round and round in circles. It lasted for about a minute. She then stood in one place for about 15 minutes and didn't move. She was breathing very heavily. I have just checked on her again and she has moved into a nest but is stood up. She looks to be clenching her bum. I can only see her from the back and I don't want to disturb her. She was fine yesterday she hasn't been I'll and no other chickens have any illness. She is with another hen and two young. Anyone know what it could be?