Craig, you are very welcome!* A leaf internode is where the leaf attaches to the branch or stem of a plant.
With the X-disease the leaves curl inward at the tips.* Peaches are prone to many different leaf spot diseases such as bacterial spot listed on that site I gave you. Do clean up any fallen leaves as soon as possible.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.