One of my chicks is constantly sleepy when the other chicks are active. They're mostly sleeping at night / mostly active in the daytime (I have a motion-sensitive camera so I know when they're inactive). The other chicks check in on her and wake her up, but it rarely leads to her heading out to eat or drink. When she is awake she seems okay, but I'm not experienced so I don't know--even when I hold her she calms and gets sleepy in mere seconds. She's in a cozy corner but fairly far from the heat lamp so I doubt she's over or under-heated (the other chicks are favoring the coolest corner, which makes sense because the air temp should be in the mid-80's in the sun room so just residual heat from the lamp should be plenty especially since they're moving around). She's also my only chick with a possible pasty butt, I've had to clean it daily (following the warm water/cotton ball method). It always seems like her vent isn't truly plugged, but there's so much stuck to her I clean it anyways.
She's an adorable buff laced Polish and I would be so sad to lose her. She's also the only one of her breed in my brooder so I can't compare her to a sibling, but they were all born in the same 48 hour period so they are approximately the same age. Any ideas to improve her outcome, or should I just relax and chalk it up to temperament?