I think it is a nutrient issue. I haven't figured out exactly what nutrient or nutrients are lacking, but I have similar growth on my lemon drop mangosteen. Since growth like that has occurred in the middle of my Southeastern summer, with its surplus of humidity and heat, I highly doubt it is an environmental issue. Like hammer524, my imbe is unaffected. But, my achachairu also shows no signs of deformed growth. My seashore mangosteens' new growth is lighter in color than their earlier growth, but the leaves are not deformed in shape.