I recently started getting into stock photography and submitted some images to Shutterstock. I was rejected for various issues like noise and focus. I was surprised at how high their standards were but I chose new images and tried again. More images passed than the first time, but some of them are still being rejected for being too soft.

The images I submitted are here: http://adobe.ly/1xmFbD8

Although I'm slightly perplexed as to how most of the images are too soft to be used (especially the pelicans), what I really want to know is:

What could I have done to get these images sharper? Do I need a better camera/lens, or is there something I am doing wrong? I'm using a Canon 60D and the 24-105mm f/4L.

The images that were rejected for softness are the flowers, take the blame, sand, pelicans, and the mountain meadow. The one with my shadow was rejected for other reasons, and the rest were accepted. I included them all for completeness.