This is a new one... burn or stain?

[jjdurrant]

I noticed a metal c-clip on my stairs the other day (no idea where is came from).. went to pull it out and I cannot tell if it got hot and burned my steps or if what I am looking at is a metal stain of some sort. Ideas?

 

[frustratedpoolmom]

Trie the vitamin c tablet on the stains to see if it's rust. Looks like rust.

I found some spots in my pool yesterday. They don't look like algae or rust. Not sure what the heck they are but I don't have a camera that will take the pics.