Without more information my first guess would be too little water and too much sun/heat; it burns the new growth. a little shade for the tree will help; more water will help, including a spritz during the hottest time of the day.

Thanks Johnmerr. I appreciate your comments.

I don't think it's heat because we are still early spring but who knows.

Could it be salt air? We are not far from the beach. Or maybe a cold snap?

I had a meiwa kumquat cutting look similar. I took a macro picture of it it it revealed spidermits. I treated the tree with the wrong thing and it turned completely brown.

{{gwi:567409}}
Check for mites.