I've been feeding Cloud BLUE Buffalo brand dry & wet food and every time I go to Petsmart/Petco I always see different types to choose, from Puppies to Adult, to Senior dogs. I was wondering, at what specific age(s) are they considered a "puppy", an "adult", and a "senior"? Even with Nutri-Cal, I still buy the "puppy" kind just because I don't really know when to change to an "adult" product since Cloud is 2, approximately almost OR is at 4lbs. And I was told that 'dog ages' vary by their weight/size, instead of the whole "add 7 years to human years = dogs age" or something along those lines. If you can, please explain...Thanks for reading my post and if you can help...