I moved this to its own thread.
Tylan is great - I would ask about a 30 day treatment in case it is SIBO/ARD.
Has your puppy been de-wormed?
How much do you feed - overfeeding is another reason for diarrhea but it sounds like you are being really thorough - it's just an easy thing to do!
I like bland/mild foods for puppies. Foods with less ingredients.
This is one of my favorites: PinnacleŽ - Trout & Sweet Potato Recipe Premium Dry Dog Food