Those pictures where rejected because of quality issues. Is it the noise or something else I can't see?
Some reasons are: Color fringing (I have never seen such wide color fringing), JPEG artifacts, missing details, color noise, oversaturated.
I need to agree with @Marianne-Deiters. You should stop over processing your files. When saving the files, you should use the highest quality possible, and you should avoid JPEG generations, as each time you edit and save again in JPEG, you're adding compression artefacts.
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
There is also another factor. That is the white balance; it is also incorrect. The sky has a magenta colour, and there is a magenta cast to the whole picture.
The pic also seems to be taken with a smartphone, so when enlarged the quality isn't good.
I suspect this was straight out of the camera, that the camera did the internal processing. With such a scene the camera made the colours too oversaturated - so the greens are too green, and this has also affected the sky.
I would bother uploading this to stock. There are a ton of photos of this waterfall. It's really famous and well photograghed.
Everyone who goes to Iceland takes photos of this waterfall!
Everybody have already given you the correct answers. In addition, the first photo is not level.
THx for all tips!