Sudden death of 2.5 year old BO hen

[Farmlife16]

She started acting lethargic yesterday and died this morning. I saw no discoloration/swelling, no lesions, and no mites/lice. She did have a messy/smelly bum, but nothing super out of the ordinary. I'm assuming she died of natural causes, but I want to make sure I'm not missing anything? Are there any signs of disease I should look for?

 

[Wyorp Rock]

I'm sorry about your hen.

Hard to know why she died unless a necropsy is performed. If you lose another in a short period of time, sending the body to your state lab will give you information. You can look up your lab in the link below.
https://www.metzerfarms.com/poultry-labs.html