Deactivated an add on in my realm and now the items from add on are replaced with question mark blocks all over my realm.

As mentioned above I had an add on but it caused some issues on my realm so I deactivated it and now my realm is filled with yellow blocks marked with question marks that replace the items provided by the add on. The previous issue had gone when I deactivated the add on but this is an all new problem for my realm. I do not believe this has anything to do with the add ons creator but maybe something to do with Minecraft’s programming.