Popcorn Anomalies

For the past 2 weeks I have been having popcorn as a late evening snack. I have discovered that 3.5 ounces of Pop Secret takes 15 seconds longer to pop than 3.5 ounces of Act II. I have confirmed that the weight is actually the same (using my handy kitchen gram scale), and they both use the same ingredients in the seasoning. Is it possible that there is a difference in the variety of corn, or where it was harvested causing the different pop times?