Pecan tree

Recently moved in to a rural area. Very rocky soil. Native trees are perennial and annual oaks, tons of junipers, and some real cedar.
Have two pecan saplings I planted in May. The one is front is in sad shape. Some of the leaves took on a brown color, but did not immediately dry out and fall off. Like it was diseased or something. There are a few sprouts with very small leaves showing near the base. The pecan tree in the back shows no signs of leaf problems. Lots of new growth near the base to about 1/3 of the way up, leaves almost full size now on this growth.
Sprayed the tree in the front with a fungicide. Seems to be clearing up the brown leave thing.
There has been little or no new growth at the upper portion of either pecan tree. This late fall or winter, should I top off both or one of the pecan trees to promote growth? Or just leave it alone?

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