Quality issue rejection - what's changed or what am I doing wrong ?

I have been submitting my images from the past fall folliage season.  Over the past serveral years, I usually submitt 400-600 images a year, and in the past have usually had about 1% of these rejected for "Qaulity Issue".   This year the rejection rate has been over 20%.  I generally spend 20-30 minutes processing an image that I submit, so I have invested quite a bit of time and effort.  I am frankly at a loss, on what would cause an image to tbe rejected.  Often, another image, that I think is very similar,  is accepted.   I have added Topaz Denoise as a more consistant past of my workflow this year, than in past years, but I think that has added to the overall qulity of my submissions.  

When I look over a rejected iumage, I am simply at a loss to wonder what "quality" caused one image to be rejected while another is accepted.   Has Adobe changed their criteria for reviewers?  What might be causing a rejection so that I can address it?