NewGen, what happened to your tree's leaves is unfortunately quite common. The damage happened way back when the leaves were just beginning to develop. Insects love the tender new growth, it is like dessert. Back when the new flush of leaves were first developing insects, most likely thrips, but also leaf miner, and and aphids quickly start feeding on the new growth. This feeding is what caused the damage. To keep this from happening again, spray at the first sign of growth with, a good horticultural oil, or even a soapy water solution. Do this every 2-3 days until the leaves develop some maturity. Even a semi forceful water spray helps a lot. If using water do it every day for the first couple weeks. With the exception of plain water, never spray a citrus tree with anything in the heat of the day. Spray either early in the morning or in he evening. These current damaged leaves will not recover, but any future growth will be fine if you follow this advice.