Me ha rechazado estas 3 fotos y no tengo claro porqué podeis ayudarme a entenderlo?

Here are the issues that I detect in your images:

Amaneceres mar-110.jpg - it's a pretty sunset, but the image has blur, artifacts, chroma noise and crushed details. Did you take this with a cellphone camera? Also, note that sunsets are already very over-represented in Adobe Stock. Yours would need to be technically perfect in order to be accepted or ever sold.

Tapas Nautico-35.jpg - Not well composed, depth of field is too shallow, causing most of the image to be out of focus, blownout area in the background.

Tapas Nautico-35.jpg - Harsh lighting, creating unattractive shadows, white balance issue (too yellow), depth of field too shallow, and not well composed.