The way I would approach this would be to create an array of actors in your game mode blueprint. In the construction script of your actors (or event onBeginPlay), I would suggest adding a reference to that actor into the array in your game mode. Then, when your player dies and respawns, you can trigger an event or function in your game mode called something like ‘resetMap’, and in here you can loop through each item in the array. As you loop through each item, call ‘Set Visibility’ and ‘Set Actor Enable Collision’ for each one.
Does this make sense? I’m not sure if I explained it very well.