We were on vacation last week and had a house sitter. She texted me that my 2 year old hen was limping, then another text the next day that she was getting worse. My neighbor came over to check her out but could not find anything. We arrived home last night and saw that she could not stand, She is alert. We have isolated her & have given her food and water which she seems to be eating/drinking.. The other 5 hens seem healthy, but worried. Does anyone have an idea of what might be causing this?