I'm not sure I'm ready to elevate my guesses to a full-blown suggestion.

I've seen marks like those 'age out' of concrete, but I don't have ANY understanding of exactly what causes those marks (I mean chemically; I know how to 'make' them), and I don't have the sort of experience that would allow me to say that what I've seen happen elsewhere, will happen to your pool.

If you can wait, wait. See if you get another answer from someone with more experience and more confidence in their answer.

I don't know if there's some sort of concrete forum on the Net; if there is, you might want to post there, because marks like these aren't unique to pools. You can use the links to the photos here. Since I put them on Picasa, it's not costing me anything for someone to download a meg's worth of image files.

If you do find an answer elsewhere, post it back here, if you don't mind.