I buy my feed 100lbs at a time and have been buying the TSC Dumor all flock, which is made by Purina. I store in a metal trash can, which gets emptied thoroughly before adding new. I put this round in a week ago and now itnhas flies coming out of it, i can see them digging their way to the surface when I scoop. Should i toss this batch? Probably 75 lbs left, and go buy new?