My twelve week old light sussex hen is very sick. She was fine when I let her out this morining, whilst out in the garden just now I noticed that she and one of the other hens had gone back into the coop, I checked to make sure they were ok, and she sat in the nesting box and didn't move. Normally she would flap about. We took her out and checked her over - no signs of injury. She's breathing heavily, sometimes with her mouth open, sitting still with her head drooping as if asleep. She doesn't want to eat or drink, but when we insist she does manage to take a few steps before going back to sleep. I can't see any other signs of illness, but I am new at this! She was treated for coccidiosis several weeks ago (full recovery) and has been wormed with verm-X 3-4 weeks ago Any suggestion? Thanks!