Slight off odor, why now?

I brewed a american nut brown ale in Feb. did the 1-2-3, and have been enjoying a beer afterwork for a couple of weeks. Last night, my beer had quite a bit more head and a slight off odor to it, taste was alittle different but not bad. I just think it might have been that particular bottle. If I happen to open another this evening and it has the same off smell,what could it be? like I said I have enjoyed the previous few with a problem. Would bacteria growth be showing/tasting/smelling this late? This is my first brew, so I'm new to the changes my HBs will go through, any advice will be helpful and appreciated.

See what happens when you open another bottle. It's happened to me before, where I didn't mix the priming sugar all that well and some bottles came off more carbonated than the others. Or maybe it was one of the bottles from the "bottom of the bucket" and has some hop particles floating in it???

I think you might have nailed it, I just got to opening another hb(why so long between beers? you wouldn't believe it if i told you) and it was fine, actually it was great! Perfect carbination, excellent flavor, down right good. Next time I'll mark my bottles so I will know when they were filled( early, middle, last of the batch). Thanks for the support. Happy brewing!

It's also possible that you had a dirty bottle. I cut the loop off the end of my bottle brush, and chuck it into the makita cordless. Just give each bottle a couple twirls, then inspect visually when rinsing. Some bottles that have been left standihg can have a ton of hard to remove gunk inside. Being your first batch, you probbably had some of those.