There was recently a leak in our shower on the main floor that was fixed when it was discovered, but it had to have been there for maybe a month. It wasn't a huge leak, and it ended up mostly draining into the basement below without running into too much along the way. I have no doubt some of it could have gotten into places for things to grow. The leak was fixed at least a month ago.
Just now I was in the basement and noticed what I think might be mold. It's in the general vicinity of the leak and you can see old water stains from what I would assume was that leak. This appears to be fairly isolated as I don't see anything similar to it or what other forms of mold look like. The best way to describe the substance is clumpy or sooty. I accidentally poked it and it fell apart like soot does. I haven't done anything with it yet, but I'm assuming it is mold. There also isn't any smell of mold down there or near it either.
Given the small quantity of it, would it be considered a DIY job, or should I call someone?