What would cause my apartment to suddenly have silverfish?

In the last 15 hours of so I have found 3 silverfish wandering my apartment. I live on the third floor and this is the first time this has happened. About 8 months ago I found a centipede but that is it for bug problems. One was crawling across the living room floor, one was on the wall in my closet, and the other was on the kitchen floor. They're everywhere. Im terrified of these bugs and I'm wondering why they would suddenly show up like that. Any ideas?