How to i get my b string to stop buzzing?

My guitar, a seagull, has been perfect for 2 years, but today for some reason i played it and the b string was buzzing, , before it was sounding crystal clear, is it my strings needing to be replaced, or something of that nature, idk but its really annoying so thanks if you can help. Some of the others also started to buzz slightly, but its unnoticeable