The interior will die over time. As the tree get bigger and the canopy moves outward, the whole zone of foliage moves outward, and the inner most foliage closer to the trunk dies. Foliage needs light to live, and as long as you see that the eldest foliage is that which is dying, and the outer, newest is thriving, that's normal. The outer dead tips are probably evidence of finishing the tree for selling. Normally you do that kind of tip pruning in autumn and new foliage grows beyond those tips in spring and all is well.