They look (to me) like some form of plant bug or possible a beetle, can't see them closely enough to distinguish. In either case, they're not beneficial. Though they may have nothing to do with the citrus, dunno.

They are SUPER tiny and hard to photograph. I even looked at them through a jeweler's loupe. One is round and the other is round but has some hair-like thing sticking out. Since they've just appeared I figure it can't be good. ugh

Great idea. I'm thinking they are eggs of some sort, but no idea what!

Do you have a magnifying glass? You should be able to determine if they're eggs or animate.

Looks like black scale.

They are most likely Stethorus, very small lady beetles, which help get rid of spider mites.

Would be a good idea to hose off the tree every several days. Plain water works well.