Lethargic pullet with fever

[Molnut]

I have a 19 weeks old pullet that is displaying signs of illness. The other pullets of the same breed seem fine. The pullet in question seems smaller, her comb and wattles seem a little darker and withdrawn, her shanks feel warm and she had a little bit of mucus coming from her left nostril. On the plus side, she's eating, has no discharge from her eyes and is not sneezing. The other odd behavior is that, while she can stand, she favors sitting and will sit after a few minutes even when eating. She seems to sit leaning more on one side than the other. I have not observed if it's always the same side.
I should mention that I have been introducing layer feed in the form of mash mixed with their crumbles early this week.
I am at loss with this little one. Has anybody experienced this kind of behavior? As she is not laying yet, any egg-laying issues can be written off, I believe. Thank you

 

[Wyorp Rock]

I have a 19 weeks old pullet that is displaying signs of illness

The pullet in question seems smaller, her comb and wattles seem a little darker and withdrawn, her shanks feel warm and she had a little bit of mucus coming from her left nostril. On the plus side, she's eating, has no discharge from her eyes and is not sneezing. The other odd behavior is that, while she can stand, she favors sitting and will sit after a few minutes even when eating. She seems to sit leaning more on one side than the other.

I'm sorry your pullet is not well.

Can you post some photos of her?
Was she vaccinated for Marek's?
What does her poop look like?

I would check her crop first thing in the morning before she eats/drinks, look inside her beak for any yellow/white lesions or sores.
Mucous coming from the nostril, is it thick or watery?
The not wanting to stand but still eating/drinking is concerning. I would get some poultry vitamins into her.
What breed is she? Has she started laying eggs? It might be worth a try to make sure there's no egg stuck.

Marek's and/or respiratory disease comes to mind with some of her symptoms. If you can take some poop samples to your vet for testing, that would help rule out worms or coccidiosis overload.