Aesthetic appeal is subjective. Maybe the second person didn't find them as appealing.
However, (and I think this is much more likely) between the time your images were accepted and now, tons of other photos have been uploaded from thousands of other users. Some of them are probably very similar to yours, but are either visually better or more commercially useful. Thus, what was acceptable previously is now no longer good enough. It's like pictures of flowers. There are just way too many of them on Adobe Stock. Someone uploading a decent flower image that would have been accepted in the early days is now going to be rejected unless it has something amazing about it that makes it stand out.
Thanks, Szalam. I could accept the 'more likely' answer if it were one or two or even three. But a dozen photos which include cityscapes, architecture, sunrise, a river scene - a variety of shots? Also, they all were rejected within a two minute time frame, according to the time stamps on the notification emails. So comparison with very similar photos from others seems a stretch. But then, I am new at this.
Is there any recourse (resubmission with hopes of getting another reviewer) or is one reviewer's opinion (maybe the second person didn't find them as appealing) the last word?
Take a hard, critical look at your images. Maybe get some advice here on specific ones.
Then, adjust the crop, color, etc. as needed to improve the aesthetics and usefulness of the image.
And then try to resubmit the ones you think would be useful.
Keep in mind though that some images that make good art don't make good stock.
For example, the stairway image you've shown here might not be particularly useful as a stock image. It's interesting visually, but more in the abstract sense. I don't know how I would use this in a stock situation.
All of the attention is being drawn up the stairs into the upper left of the image and around the corner. Interesting artistically. A lot could be said about it.
However, if you put content anywhere on that image, it would be away from where the image is trying to draw your attention. Thus there would be compositional issues. Also the image isn't really "of" anything - there isn't a story in your image or really any metaphor. It's just some stairs. So you couldn't really use it in a frame with text outside of it either because it really doesn't represent anything.
Again, it's a nice photo and I could stand in front of it and discuss it length in an art gallery or a photography show, but I can't think of how to use it in a stock context.
Thanks for your time. I appreciate the detailed response.