Welcome !!!! Just be careful when changing food with your puppy it is hard on them and you should (if you are not already) be mixing the new food with the old food as to wean them. Start with a 80/20 blend then go to 60/40 ect..  when change their diet it will give them lose stools unless you take them off gradually. For itchy skin you can also introducing Brewers Yeast, this has omegas to help with their coats and skin. One other thing that can cause itchy skin is bathing, dilute your shampoo down, rinse well and use conditioner. We all bath are yorkies often, due to the fact they have a coat similar to our hair. But the shampoos can dry out their skin and cause them to itch.
  We are glad you joined and will be looking forward to your posts.