go burp on the smoke alarm and see if you could set it off.....my brother set the alarm off in my grandparents camper with some serious ass stank once.....true story.
You shouldn't be. If that's happening they've probably gone slightly rancid and need to be discarded. At the very least they're no longer supplying the nutritional value they originally did, and they could even make you very sick if they continue to spoil further.