Resource guarding is a fairly normal behavior that we humans tend to make worse when it is quite easy to make it go away! Although we have done some preventative training with your puppy already, you should be aware of this concept if you see your puppy freeze, growl, lunge, etc over any item as you approach or reach for it. DO NOT PUNISH THE PUPPY. That is the golden rule, and the primary reason this gets worse instead of better.
Here are two good articles:
Also, be sure to watch my video at the bottom of this webpage for a demo!