Dash is now over 10 months old and hes never exhibited any signs of aggression until this past week. Our other dog and Dash have always shared toys and treats without any issues. Recently, when another dog or even sometimes another human goes down to his level while he has a treat or eating, he begins to growl and show his teeth. Ive never had this issue with any of my other dogs, and I dont have a clue on where to start to correct it?

Suggestions and advice please.......