I cant help you with what to do for your tree. I'd like to know how long did it take to get that big? I've got a couple of babies growing that I started from just putting seeds in a pot :>)
Christine

The pot looks awfully small for that tree.
Are you fertilizing? With what, and how often?

Josh

The tree is probably 5 years old? Maybe a little more. I repotted it in February from a 6" pot. I only fertilize it in the spring and summer with either a 5-1-1 or 15-15-30 every two weeks.

You could have Citrus Leaf Miner, they get in under the "skin" of the leaves and normally insecticides can't reach them. White oil is recommended for that as it leaves a layer on the leaves and discourages the adults from laying eggs on them. It doesn't do anything to the insect larvae inside that are doing the damage. Damage to the leaves is permanent. Another option is to cut off the affected leaves and burn or dispose of wrapped in plastic. Trouble is that there's still often some adults around to keep the cycle going.

It could also be a trace element deficiency. There is citrus specific fertiliser, or just make sure what you use has the trace elements. Copper is important for citrus, one of the old timers remedies was to put a copper nail into the trunk of the tree. Copper nails were used in timber hulled boats so they were readily available back then.

If the leaves grew warped like that because of a spider mite infection, they still won't go back to normal after the mites are gone.
The leaves have just grown malformed and they'll stay that way.
If the new growth is normal, you needn't worry! (:

- Sparkey

Tropicbreezent, I doubt it's some sort of citrus virus. I'm over 2500km from the nearest citrus patch. The leaves turned all gross over the winter. Hopefully this summer the plant actually grows or it's being left outside for the frost.

I'd fertilize it. Iron and Calcium, and of course Nitrogen.
If you haven't supplemented with iron and calcium yet, that's the first thing I'd do.
Citrus need nutrients year-round.

Josh

Will, I didn't say "virus". But yes, if it happened during winter in your climate then it wouldn't be Citrus Leaf Miner, the adults wouldn't be active then. But trace element deficiency is still a definite possibility.