Any specific things I can work on to get my pictures approved?

Red cup -- harsh lighting, oversaturated color, possible IP issues.

Clock tower -- underexposed tower, possible IP issues.

Fishermen -- main subject is dwarfed by all that water, pictures of people require model releases. 

Before you submit again, read through your Contributor User Guide.

Start with the 4-part section on photography requirements:

1. https://helpx.adobe.com/stock/contributor/submit-your-content/submit-photos/photo-submission-overview.html
2. https://helpx.adobe.com/stock/contributor/submit-your-content/submit-photos/technical-legal-requirements-photo-submission.html
3. https://helpx.adobe.com/stock/contributor/submit-your-content/submit-photos/photo-editing-best-practices.html

Good luck.

Hello,

A few issues - colour balance, exposure, composition…

To improve, learn a bit more about photography. 

For a start, read about composition:

Composition

There are focus and/or exposure issues in all of these. I would t even bother with floral images. Query the database for “pink rose” and see how much competition there is…

Please check the image on your PC screen at 100% zoom before submitting.

Flower
Blurry

Clock tower
Excessive noise

Vase
Out of focus

Lake
Out of focus

The clock tower is under exposed, has a green cast, and the tower itself is slightly slanted. The pot is underexposed and oversaturated, with a reddish cast.