For a measured response to your query, please go to the link below. Copy & paste the text into a new post in this thread & include answers to all of the questions. With more information it will be easier for people to answer your query.http://forum.backyardpoultry.com/viewtopic.php?f=5&t=7955698
On first appearances, the lack of eggshells would generally be due to a lack of calcium. Upping the calcium in the chook's diet will fix that very quickly... sometimes within 24 hours. The drooping tail, together with a 'classic coccidiosis stance' could indicate that you should treat for coccidiosis. If you look in the 'stickies' in the GSMC (Good Samaritan Medical Centre) you'll find links to threads with photos of the classic pose (which isn't always seen in coccidiosis, but is a good start)... here's the link to it to give you a shortcut; http://forum.backyardpoultry.com/viewtopic.php?f=5&t=7975815&p=267835#p267835
Before you do that though, go to the post mentioned as it will ask for far more detail in order for people to be more accurate in what might be wrong (whether one thing or multiple things).