Alt Tags Not Updating

Hi all,

I have over 600 images that I need to optimise with a Title and Alt Tag. These have already been uploaded and were not optimised in any way.

However, updating within the Media uploader seems to have no effect. The changes show but when the pages are run through an Alt Tag checker with cleared cache the changes do not stick.

This site uses custom templates and advanced custom fields plugin on a Twenty Eleven theme 1.3.

Even when I update the tags within the images/gallery fields within the ACG plugin it has no effect.

I have deleted images off a test page and reinserted but this had no effect either.

I suspect its a php issue but not sure where to start, the theme, the custom template php files ? And what do I need to change to make the Title & Alt Tags stick for each image as I work my way through them.

Thanks for any help

Stem