8 years ago I planted three peach trees from the Arbor Day Foundation and they began wonderfully. One took off like a shot, another not so good, and the third croaked. Of the two remaining, I seek more know how of the proper maintenance of the peach tree. Number one, the big'n, keeps producing and never fulfills with completed fruit and has needed trimming back from lack of strength in limbs to support weight and suffered some branch breakage. I am unaware if there is anything that will help in the focus of the tree itself strengthening its own limbs or if I need to add any "special" type fertilizer instead of a general equalized fertilizer to the roots for the limbs getting tougher so that they will be able to support what they produce.
Here are some links that will help you.