My EE hen, Thelma, is nearly 3 years old. Over the past several days she has become increasingly lethargic, not following the other girls out of the coop as quickly in the morning or showing much interest in normal chicken activities. Today I observed her for quite awhile in the morning, and she just stood in one spot for a long time, tail down, head drawn in, and looking a little puffed up (it is cold here in Colorado, although they have a heated coop). When she began to move around, several times she squatted and strained like she was attempting to poop, but only a couple times did anything come out. The poop looked normal, but it was extremely small. I picked her up and examined her, and I couldn't feel anything in her crop. I didn't see her eat or drink anything with the rest of the chickens. Her vent looked normal. There was no redness or bleeding and no poop crusted on. I felt her abdomen and did not feel any swelling, hardness, or squishiness. She is an older hen and has not laid for several months, so I don't think she's eggbound. I couldn't find any other abnormalities. Does anyone have any idea what may be causing this? I've searched and searched for answers and I'm stumped.