I am fairly new to raising roosters I've only had two. Chuck and now Charlie. Both Rhode Island Reds. Chuck died. I have no idea why, my best guess was he got food stuck, but he gave me Charlie. I raised Charlie from an egg and spent a lot of time with him as a teenager. I pick him straight up...
https://www.chickensandmore.com/isa-brown/
Sadly, it looks like you're right. This was a sweet article so I'm sharing it for you and your beautiful Isa Brown. 💝