Your baby is sooooo cute, and the boy too for that matter. I think it is the puppy coat, and if you the last week or so have a warmer weather than you did before, that is probably also playing a role in this. Of course it could be the change of food, but I dont think you have to worry about that, especially not with such a high quality food, having said that, you can get the best of foods and some dogs still develop allergies or other problems.
But being the age he is and that you said that it seems to take a long time for him to grow his adult coat, I think warm weather might have boosted his "puppy coat blowing" so thats what you see.
Good Luck and hehe I dont want to be a party poop, but hair around the cage, well hmmmmm it might just get a little worse still lol....
Marit