Please guys, could you critique some of my photos?

You need to be care ful of your composition. You cut off the nose or cut off the hoofs. Avoid identifiable objects in the background and you will not need a property release. Do post production clean-up on exposure, color and composition.
Have a look at some of my animal photos:
Ralph Lear Masterclass Outdoor Photography - Animal Photography

Hello,

Photography involves quite a lot of thought to take a good photo. Not only lighting, exposure, and the right type of aperture for the shot, but also composition.

I think you could work on improving your composition.

Read about composition in this link.

Composition:
https://www.adobe.com/creativecloud/photography/discover/photo-composition.html

PNG is for images that contain transparency only.

Photographs must be submitted as sRGB JPEG files, not PNG files.

Adobe Stock customers expect the highest visual and technical quality for use in commercial projects. Snapshots are OK for sharing with friends & family on social media, but they're not good enough for commercial use. 

Read your Stock Contributor User Guide for more tips on what's expected. 

• https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html
• https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html
• https://helpx.adobe.com/stock/contributor/user-guide.html/stock/contributor/help/photography-illustrations.ug.html
• https://helpx.adobe.com/stock/contributor/help/how-to-submit-distinct-content.html
• Model/Property Releases:
  https://helpx.adobe.com/stock/contributor/help/model-release.html
  https://helpx.adobe.com/stock/contributor/help/property-release.html
  
  

You should submit your images jpgs, not pngs. pngs are reserved for images with transparency. It also looks like these were taken at a zoo or on private property. You may need a property release to sell these images commercially.