I am having an issue where my players can see homebrew spells and item. I did not add these to my collection so I do not understand why they are able to see them. I thought that if they are in my campaign then they are limited to the homebrew items they add to their collection or I add to mine. They are seeing options that neither of us added. 

Someone in the campaign must have them in their collection somehow. Each one might be in a different person’s collection, because everything in everybody’s collections gets shared with everybody in that campaign. But each of them must be in somebody’s collection.