hen seeming overly tired?

can someone tell me whats wrong with her? Her feathers look less smooth than normal and she isn’t walking, if i pick her up and set her down, she will maybe walk two steps and slowly sits down again. Shes been eating and drinking but not moving well, tail down, and looking hot consistently. I did recently move and brought her and two other chickens but shes the only one that doesn’t look healthy and normal. Shes been resilient for such a long time that now that shes looking weak im worried im racing the clock against something i cant even diagnose in time.