I can finally see the photos. I was having that problem throughout the entire website. The black spot looks like a blemish on the pearl. It's not related to dyed vs. not dyed. Most of the time, vendors try to put the drill hole at a blemish, but if there is more than one blemish and they are not on opposite sides, then one of the blemishes is going to show.
I can't tell from your photos if these are dyed or not dyed. There are akoyas that are naturally that color. They are not well matched and they need to be restrung, and a good wash would also perk them up.