What was the rejection reason given?
So, in your image, you have issues with the quality of the pixels. If you zoom to 100 or so percent you can see this:
They appear a bit 'blocky'. So, another rejection reason could be 'artifacts'. That is a common refusal reason as well.
Also, I think, your exposure is a little underexposed on the flower. You could add more exposure to the flower and then bring down the highlights.