I want fresh feed all the time, and would wonder about mill dates on feed being shipped from an outside source, like Chewy. Check those mill dates!
Around here, TSC usually has fresh enough Purina Flock Raiser, and the local feed store that stocks Kalmbach keeps that feed under a roof but...
Do you always check the mill date on each bag? Make sure you do that, and feed within two or three months of the mill date. Then, storage is important. Your deck box is okay, or not? Dampness is so not good!
If it's not a problem with your container, it's about Chewy somewhere, old feed and...