Let me add that the tracks are *light* brown, and there is no yellowing around them nor anywhere else on the leaf.

It could be leaf miners. While the fresh burrowing of them inside the leaf shows white the lines do fade with age to a light brownish color.

So check some pictures of leaf miners and see if the pattern is similar to what you have.

Carolyn

Hey Carolyn, I think you've got something there! I googled pics and that's what it looks like. Come to think of it, yesterday I found a tiny green worm flopping around on the balcony nearby the plant and didn't think anything of it (I did squish it though).

Now off to figure out how to deal with the critters. Thanks!!