Reason for rejection

To take photos for Stock, you need to know what you are doing and you have to think about their commercial use.

Perhaps read these links from Adobe.

User guide:
https://helpx.adobe.com/stock/contributor/user-guide.html
Exposure:
https://www.adobe.com/creativecloud/photography/discover/exposure-in-photography.html
Composition:
https://www.adobe.com/creativecloud/photography/discover/photo-composition.html
Learn and support:
https://helpx.adobe.com/support/stock-contributor.html

Artist hub:

https://stock.adobe.com/pages/artisthub/get-started

blue fish: not sharp, the composition is not great. The white balance needs correction. Reflections on the stones are disturbing. 

rare bird: the white balance needs correction, the asset is not sharp. 

tiger in wildlife: the tiger is not sharp. BTW: the tiger is not in wildlife, you see that the environment is set-up. 

The girl: is not sharp. As with all of your assets, the details are dull. The flowers are a red blob. The set-up with the girl sitting, head turned back is not appealing. You will need a model release for the girl.

As for the others: I suppose, they are all the same. The whole looks like a zoo visit with your girlfriend, doing snapshots with your phone camera. It does not look very commercially appealing.