After being gone for a couple of hours last evening, we got home to discover that one of our 4 hens, Wilma, was suddenly failing. She hadn't made it up the ladder to the henhouse for the night with the others and when we picked her up, her comb was pale and she was incredibly weak - just limp. She had been up and bouncing around with the others the day before - she had even laid the day before. Her vent looked clear and fine, her crop felt fine - we didn't know what the deal was but we prepared ourselves for the worst. We isolated her in the garage with a little heat and put some food and water in a big dog kennel, made a little bed of straw for her and watched her on and off through the evening. She just worsened as the evening went on. When we went to bed, her breathing seemed a bit labored...she couldn't even lift her head. I woke up early this morning and went down to check on her expecting to find a dead hen in the kennel, but instead I found her up and clucking - drinking and walking around! I couldn't believe it - so I brought her a little dish of yogurt and will scramble an egg for her in awhile to boost her protein a bit. What could this be? (Wilma is an 8-month old BO.) Is there anything I should do before putting her back out in the coop with her sisters? Should I keep her isolated for a couple of days?