I have a 3 y/o black sexlink hen who up until last night was eating and drinking lots, but this evening can barely move, won't/can't eat and drink, has mucus coming out of her beak and is very un-responsive. Her crest is a dark red colour and is drooping over, she is very thin, and a relative...
I don't know exactly where you live, but it may be because of the cold. You could try adding more protein to her diet.(May work, may not. I'm no chicken farmer.) All chickens behave differently-One of my hens just passed because of pneumonia, and the other was/is just fine.
One of my two hens just passed due to pneumonia, leaving just one hen who is used to having a buddy 24/7. The hen that we still have left has never been sick, we are guessing she has a stronger immune system. We are looking for a new buddy for her, but we want a hen who has a better/stronger...