When a fellow chicken keeper posts a plea like the one from /u/graveyardfairies, you can almost feel the knot tightening in your own stomach. She describes a hen who was "resilient for such a long time", the kind of bird you start to believe is invincible, and now that bird is moving slow, tail down, and looking hot. The feathers have lost their smoothness. She eats and drinks, but she won't walk more than two steps before sitting back down. That's not just a bad day. That's a signal, and it's terrifying because you don't know if you're racing a clock you can't even see.
Our honest take? This is the part of chicken keeping nobody wants to talk about at the feed store. The move you mentioned is a massive clue, relocation stress can trigger latent issues in even the toughest hen. But the specific combination of lethargy, heat, and a drooping tail points toward something more urgent than simple homesickness. It could be reproductive trouble, like egg yolk peritonitis or a stuck egg. It could be an internal infection or even a digestive blockage. What it isn't is something you can fix by waiting it out. Your hen is telling you, in the only way she can, that she's running on empty. You did not fail her by moving, you gave her a new home, but now you have to act like the detective she needs.
So what would we tell you directly? First, stop guessing and start checking the basics that are free to do right now. Feel her crop first thing in the morning before she eats, if it's hard or doughy, that's a problem. Look at her vent: any swelling, discharge, or straining? Pick her up and listen to her breathing. A gurgle or a rattle means the clock is ticking faster. If you can get her to a vet who sees birds, do it today. If you can't, then separate her in a quiet, cool space with electrolytes in her water and a shallow bath to bring her temperature down. Do not force-feed her. Do not assume she'll bounce back because she always has before. Resilient birds don't give up easily, which means when they finally do slow down, they're usually fighting something that's been hiding for a while.
Here's the concrete part: you have maybe 24 to 48 hours to make a call that matters. If she worsens overnight, you will have to decide whether to let her go gently or push for a diagnosis. That is not a sign of failure, it's the hardest part of loving something that can't talk. Your hen trusted you enough to show you she's weak. Trust that honesty, and give her the dignity of a decision made with clarity, not panic. You moved her to keep her safe. Now you get to prove that safety means more than just a new coop.