Anyone have any ideas why they would all come from the same range as me?
Yup. Two possibilities. The most likely one is that your subnet neighbours suck at AV and are infected with worms that are looking for new places to propogate to. Hug your firewall. It's doing it's job by notifying you.

The second one is that you have subnet neighbours that have too much time on their hands and are playing with one or more of a variety of port/vulnerability scanners in hope that they find something vulnerable. Again, hug your firewall. It's doing it's job.