On Friday, March 29, 2019 at 10:15:57 AM UTC-4, condo owner wrote:
Here are more photos:

https://st.hzcdn.com/simgs/c132db930...ome-design.jpg
https://st.hzcdn.com/simgs/459226720...ome-design.jpg
https://st.hzcdn.com/simgs/140228500...ome-design.jpg

If I had to guess, I'd bet that it has something to do with how they
were manufactured, that those areas are somehow different, eg the
material wasn't fully mixed, etc. I'm more confident that it's not
something that's on them, than you can remove. You could try working
on one area of one that's not in a main viewing area. Try a nylon
kitchen scrub brush, working up to steel wool, sandpaper etc and
see what happens and how it looks. You might be able to remove some
of the material, exposing something better underneath. But it's also
possible the nice finish is just on the top, who knows....