Sorry you haven't had a reply. Clearly everyone is stumped. I grow favas every year but have never had this happen. You could check chocolate spot and anthracnose which favas get over here sometimes. There is also rust but that doesn't make the leaf tips go black. Have you grown favas before? The do have natural black splotches on the flowers. That's not what you are referring to is it?

A photo of the problem might help.

I don't know if it is the same problem.

But we had some early, almost summer weather for a few weeks. My favas started growing fast.

Then we had several hard frosts and the leaves turned black. It killed a lot of my plants and stunted the rest.