maya-this could have been the problem with xs growth. I have seen it happen with other kinds of trees.
They are on light soils, and I used the Ed method of adding black dirt, and one bag of compost to the hole. I usually tuck in a couple small handfuls of chicken bedding/manure on the very edge of the hole at planting, keeping it away from the roots. I will look at the other trees I planted last spring in the same way, but did not notice any problem.