Are you referring to the brown, hanging structures on the tip of the branch in the center of the photo? Those are the pollen cones, reproductive structure of the tree.

These pollen cones appear only on one of four trees in a row - just timing issue?

That suggests that you have some genetic diversity among your trees, which is a good thing! Trees are a little like people, in that they mature at slightly different rates. The tree with cones has reached what we term "reproductive onset" a little ahead of the other trees.