Hi @chloroform thanks for the reply. You are correct for paid subscription Journals like Cell, Science and Nature where you need the Journal and Author's permission, but the PLoS Journals are Open Access and all PLOS journals applies the Creative Commons Attribution (CC BY) license to all articles and other works they publish. From the PLoS website:

If you submit your paper for publication by PLOS, you agree to have the CC BY license applied to your work. Under this Open Access license, you as the author agree that anyone can reuse your article in whole or part for any purpose, for free, even for commercial purposes. Anyone may copy, distribute, or reuse the content as long as the author and original source are properly cited. This facilitates freedom in re-use and also ensures that PLOS content can be mined without barriers for the needs of research.

Originally I was using pixabay.com images that have the CCO licence so I changed it to Creative Commons licensing as it encompasses the various licences. I fixed the attribution for the images.
Cheers!
ian