Sorry about not answering right away, we are on a road trip and don't always have reliable internet.
Anyway, I see the issue only with that lens and it is pretty clear from looking at it that the problem is right at the front of the lens, although it is hard to tell where exactly. It could well be a fungus, never thought about that but the appearance of the "cloudy spots" might support this. I'll see whether I can open the lens and clean it, if I damage it so be it, it is pretty much useless at it is.
Thanks for the link to the article, I'll check that out as well.