Can anyone tell me why my young mango leaves look like this? The tree

was planted in Phoenix, az last fall and gets intense watering per instructions of the tropical tree seller here. These leaves are the new ones put out in the last month or so. The older leaves are a good dark green. Earlier in the summer a lot of the avocado tree leaves (also young, planted last fall) looked very much like this. The tree is under shade per seller's instructions.