Why is my puppy always licking something?

[nymph]

My 3 month old puppy Golden/Lab mix puppy Diego started to lick almost everything since a few days ago: furnitures, the floor, my appliances, the doors, my cloths, socks, and us. Other than sleeping, he's always licking something. He's on Nutro large breed puppy chow and he gets his daily intake of fatty acid supplement (one pill per day) and 2 tbsp of yougurt with active bacterial culture, and a few other treats like cheese, baby carrots, ice cubes and kibble treats.

He is crated 8 hours a day, but my husband comes home during lunch for about one hour to feed him and let him out. He also sleeps in the crate right beside our bed.

My question is: why is he constantly licking? Is he bored? Is he missing something in his diet?