HDRI = Unwanted reflections on the my floor

Hello - I apologize if this has been answered - I did look before asking…
I am new to UE - using ver 4.26. I have added a HDRI backdrop to my scene (a simple room, using a hollow box brush with textures applied). When I add the HDRI backdrop, it works fine - I can see the background through the windows I’ve created - BUT - I am seeing the cloud reflections on the interior floor. How can I prevent that from happening?