Lost a calf yesterday, don't know why

Lost a 12 day old calf yesterday and don't know why.

Calf has been thrifty, but found her laying curled up and looking peaceful.

Posted the calf.  Heart looked large.    Heart walls were thin.

No trauma, no lesions anywhere.

Digestive tract and contents were normal in appearance.

Coloration looked right.

Waiting for test results from organs.

Vet said too young for black leg.

Any suggestions?

Interesting find with the heart, have you heard anything back from the tests of the organs? You've got me curious!

No news yet from vet.