I definitely see some fresh citrus leaf miner trails in the far left leaf, but the black stuff? Can you magnify at all?

Really need a closeup in focus. I would guess aphids though. They hit the newest growth and cause lots of curling on the developing leaves. Aphids should be fairly easy to control.

Psyllids will attack stems as well as leaves.

I stumbled across a nice page with pictures showing common citrus pest & problems. maybe this will help id things.

https://extension.uga.edu/publications/detail.html?number=B1520&title=Maintaining%20Commercial%20Citrus%20in%20Georgia

Excellent site for discovering pests, and problems. Leafminers, and mites seem to be the ailment for my tree. Here in SoCal they've just quarantined a large area for Queensland Fruit Flies. Had the Ventura Ag Dept come out just to make sure on the Psyllid.