Help identify this disease Wyandotte

[Guinea girl 123]

Hello everyone. Thank you in advance for the help, this little guy died this morning from whatever this is. He was lethargic for one day and died the next morning. I want to know what it is so I can watch for it in the rest of my flock. Thanks again

 

[Eggcessive]

Sorry for your loss. How old was he? Can you give some details of his symptoms? Did he eat and drink, and how did his poops look?