All photos rejected due to technical issues previously approved by Shutterstock

Well, I suppose that the Shutterstock moderator did a bad job, at least for the first and the last picture. The first is out of focus and the colour fringe let's me think of a strange processing problem. The last one, with the flags of "la grande nation" has chromatic aberration. One of the nuts pictures is overexposed respectively has blown out highlights. All this just by looking at your pictures on my iPad. Next year, I will probably do a more detailed follow-up, if there hasn't been one in the meantime. 

If you are new to stock, you should consider these resources: https://helpx.adobe.com/stock/contributor/tutorials.html
Please read the contributor user manual for more information on Adobe stock contributions: https://helpx.adobe.com/stock/contributor/user-guide.html
See here for rejection reasons: https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html
and especially quality and technical issues: https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html

Because one stock agency accepted the photos, doesn't mean every stock agency will.  I have certainly have had photos that were accepted on one and not the other.  I have just come to terms with it and try to figure out when my photos are rejected how I can do better.

With that said, I would think these are the things that could use improvement:

1.  Not enough of the flower bloom is in focus and you have strange fringing / halos in the sky along the other flowers

2.  Noise and some blown out highlights in your main flower stalk

3.  Vignetting and uneven exposure in the nuts

4.  Vignetting and white balance issues (seems to yellow), the lighting / flash on the nuts seems blown out

5.  Uneven exposure (left seems under exposed, right seems over exposed) - there may also be an IP issue with the tower

6.  Exposure issues again and the window would look better if it were level

7.  Sky is blown out with no details, soft focus on the balls and probably an IP violation as this is probably considered someone's art installation.

I hope this helps you out.

-Rob