James,
Then update the responsive grid, press button and check settings of the pages.

You probably changed something and x5 just let's you know that they have chenged settings, so check if this is still the way you would like it.

Also be aware of empty spaces on your pages, it's best to avoid them, they slow down as well and are not needed, you can align the objects with the style button to be placed as you wish.

This will speed up a lot.