Problem with swiping between pictures, or changing to next video

I need some help with a problem that has started recently.

I use a file manager (Root Explorer by Speed Software), but whenever I try to view pictures in the gallery app (QuickPic), I find that I can only view the picture that I have clicked on, and I am no longer able to scroll through the other pictures in the directory.

The same has happened with videos. If I have more than one video in a directory, I am finding that I am no longer able to skip to another video in the same directory from the video player app (MX Player Pro).

I don't know if I have altered a system setting that causes this. Its as if the directory information isn't being passed to the video or picture viewer apps, and as if they don't know that other videos or images are in the same folder.

Thanks for any suggestions that might help me fix this. Its not a major problem, but is irritating.

Jonathan.