Is it normal to be spotting after being on birth control for over a year?

I was on Yasmin for a year and I've been on Yaz for several months now. Honestly, the whole time I've been on birth control, I've only really spotted at the very beginning. I had my period about one week ago. It ended on schedule then, a few days later, I started spotting. It's pretty heavy for the spotting I'm used to but it's not nearly as heavy as my regular period. This happened to me last month, too. Is this common with Yaz?