Could be a host of things... too much fertilizer, too little; too little water; insects (maybe spider mite)... No way to know without fotos. If you post some fotos of the plant and some of the leaves, there are experts here who can give you advice on what to do. First, where do you live; is the tree in a pot or in the ground; what is your water/fertilizer schedule... basics that allow someone knowledgeable to give you an educated answer to your problem... FYI, in the future I would buy your tree direct from Fourwinds growers... google them online; you are more likely to get a strong healthy tree... that assumes that you don't live in one of the states where Fourwinds is not allowed to ship

Letting those young trees fruit is a big mistake. The growers trick the young trees in to fruiting as it helps to sell them but it is horrible on the tree. If you allow the tree to keep those fruit at planting it normally ends up that the tree the following year will produce no fruit.

Instead of spending the previous season growing roots to support the tree the energy went in to growing and ripening those fruit. If it were my tree I would not use any chemical fertilizer on it at the moment. As a rule chemical fertilizer tends to make unhappy plants even more unhappy. I only use chemical ferts on happy growing plants UNLESS I can clearly see from the leaves they are in need of it.

You don't have your zone posted so is the tree in a pot or in the ground? Curled leaves could be it got too dry or could be the wrong mix if in a pot and the roots are staying too wet.