Stalk turning dark color almost black

So just as the title says, what is causing that? I've looked on the internet for a few days and can't find anything. I do remember coming across a link that gave some info on my situation but that was before I had a situation and this was a few months ago.

I don't have any pix but one of my 'friends' has the top of the stalk and along almost the entire length of it, turning black. It is also starting to show on some of the leaf stems as well.

Any ideas?

Stupid fucking site!!!