white settings page

here i come in horrible english (excuse me, i’m dutch); on different settings pages of the (free versions of the) plugin (on clients sites), i have a white screen were the settings of the plugin should be (in the dashboard). when i hover over the page, i can see the tooltips en that there should be text, but it looks like the background is white and the text and lines are white.
i really really cant see what goes wrong here, anybody got a hint??!

this is happening on 2 yith plugins setting pages on the same site.