For a start, the composition isn't good. Both the flower pictures are too closely cropped - it is framed too tightly. You should have some room around the flower. Secondly, the white flower, the exposure/ lighting is bad. Using a direct flash is too harsh for such a photo. I think white balance is an issue as well with the second flower photo.
Think about your composition and lighting with flower photos. There are a lot of flower photos on stock, so it really needs to have the WOW factor, and to stand out from the crowd!
Have a read of this. It's a brief guide on image quality.
Both images has color noise and white balance issue. The white flower has purple color fringing. You may attempt to correct the noise/grain, white balance, and color fringing of the first image and resubmit. The other image is too soft at the edges. It likely will not be accepted at all.
The harsh shadows make the picture unatural.You can build a cheap diffuser and try shooting again.
The second flower is better, you didn't use the flash. But the hearth of the flower is not sharp...
Framing is bad in both cases.
I'm having the same issue but I'm learning from the answers to your post!
Welcome to the Adobe Community.
Please find attached some non-technical notes I have made.
Apologies in advance for handwriting on your work, I found it quicker and was with the sole purpose of providing some help beyond the "plain" rejection legend we all might have get once or more in our work. Photos are assumed to be yours. NO plagiarism intentions of any kind at all are pretended from my part. I hope this contribution helps to cover one part of that "big void" of multiple possible rejection reasons.
I am not an Adobe employee nor anybody to convince you about anything, I am just a volunteering dude trying to help people blowing off some steam when their work is rejected.
In other words, trying to provide an "out of the box" perspective. My contribution is with good intentions only and hopefully will produce at least one smile.
For more formal and professional comments listen to the guys that clearly know what they are talking about.
Keep shooting, learning, observing, and specially, having fun!
PS Beautiful subjects