You probably should have asked this question in the "Citrus" section.

That being said, I do know what is most likely causing your problems. Look very closely at all the leaves. Do you see any evidence of leaf miner? (do an internet search if you do not know what that means)

Otherwise it is most likely aphids. That white powdery stuff is sugar that has crystallized out of the sweet gooey excretions left behind by aphids. The excretions can attract ants, which is not a good thing, because ants have a sort of mutually beneficial relationship with the aphids (but bad for the tree) where the ants will fight off the beneficial predatory insects that eat aphids and normally keep their numbers in check.

All the moisture being sucked out of the young leaves by the pestilent insects results in the leaves being permanently disfigured.

Much Gratitude parker25mv