My hair is becoming white, what might be causing this?

First of all, I’m only 19 years old, so this is all too weird to me. Earlier today, I noticed that my hair is now growing white (!?), something that has never happened before. It’s not all my hair, but there is a noticeable amount of hairs that just stop being brown (my natural color) and yup, there we go, they’re white. Silver-like, really light white. At first I was shocked, then decided it would be pretty cool if all of it turned white, so I’m not really trying to fix it, rather than wondering what might have caused it. I have bleached my hair a few times in the past (but I haven’t messed with the roots or anything) and I was actually thinking of maybe bleaching it again (which I haven’t, and probably won’t anytime soon, since I’d like to keep track of the change). But can that cause hair to grow white? I also have a close relative whose hair became white earlier than it was supposed to, but he was in his late twenties, a decade older than me.
Any ideas?