I would appreciate any feedback regarding why these images were rejected.

Quality issues?

Composition of those pictures is bad, and composition is part of the quality requirements. There are in addition noise issues (not too much, I agree) and focussing issues. The DOF is too narrow for this type of assets. You probably need all of the flower in focus. 

Looking at the exposure: the first picture is slightly underexposed, and then you have this: 

I wouldn't have expected this strange colour blob from your camera/lens. It's probably a kind of reflection in one of the different lenses.

But even if you would have succeeded entering these in the database: flower pictures do not sell.

I agree with @Ricky336 . Your composition is a problem. The shadowy blob of stem covering almost half of the photo has no purpose. 

Composition would be a good reason!

Composition:
https://www.adobe.com/creativecloud/photography/discover/photo-composition.html

You've cropped off part of the bloom and the stem is underexposed and blurry.

For starters, you shouldn't submit images that are so nearly identical to one another. Curate your assets first and submit the best. Outside of that, the shadows could be opened up and there is an issue with cropping.