I seem to remember that black specks were a problem with Palladio, I THINK the consensus was that it was a paper problem.
I also believe there were two problems, one where the specs were apparent after paper manufacture and the other was that some specks didn't show up until after development.
In the former case, they used to sell product with the visible specks at a big discount, that was the kind I used to buy. I never had the latter happen to me.
That's what I recall, anyway, it's been a while -- I'm sure some brain cells have disappeared. :-)