Wow, your tree is in just terrible shape. Not sure where you are in California, if you could tell us your location, that would help. Many things wrong based on this photo, which is really hard to see the tree in its entirety, but to start, it looks like you've had a serious Citrus Leafminer infestation. Search our forum for the gazillion posts on CLM and treatment options. Also, from what I can barely see, looks like your poor tree is potted in dirt and not well draining potting medium. Another huge issue. I would re-pot using a good quality bagged cactus mix, or use the 511 potting mix recipe found on this forum. You don't tell us how often you water, how often your fertilize and with what, how much sun your tree gets a day, many other things needed to give you better advice. And, being in California, any reason why your citrus tree is in a pot, versus being planted in the ground?

Patty S.

not sure if thats CLM, dont see the squiggly lines, looks like hard water deposits or fertilizer residue.

seems to be some fertilizer leaf burn on the edges.

have you fertilized recently?

are you near the coast? could be some salt burn also.

i agree with Patty about the potting soil. repot it soon and with a well draining mix.