New and young leaves remain healthy and turgid because their cells contain adequate amounts of water. Water is used by the tree to manufacture metabolites, move minerals up from the roots, in cell division, plus many thousand of additional life giving functions. The amount of water needed for the above functions, however, is infinitesimal compared with the amount transpired from the leaves. As long as the atmosphere surrounding the tree is not saturated with water vapor, the tree loses water. The drier the air, the greater the wind, the higher the temperature, the stronger the light, the faster is the rate of water loss from the leaves. New leaves have not fully developed their cuticle, therefore transpire water MUCH FASTER than do older mature leaves. Unless this water can be replaced promptly, the leaf will begin to wilt, or worse, become completely desiccated. I don't know what type of light you have, nor it intensity, nor how much heat it emits, nor how dry is the atmosphere surrounding the tree, nor the water content maintained in the soil, but evidently the new leaves lost water faster than it was being replaced. The next time you see new growth, if you regulate the trees surroundings, I'm sure the tree will appreciate it, and happily reward you with plenty of health new growth. - Millet