are redworms ok to feed to eels?

Well the reason I ask, is because I got one and it was fine, made it through the night, and even eat half a redworm in the morning. It was fine all the way into the afternoon, then I watched some tv and came back and it was belly up on the bottom and the other fish were picking at it. The other fish didn't pay it no mind untill then, it seemed fine and would swim around, and hide, and no one bothered it.
Do you have any idea, what might have caused it's dimise?
 
Unless it went from really acidic water to really base water, I don't think that would have killed it. They are very adaptable fish.

What are your water parameters?
 
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