For some reason these little strips of light come in on the corners of my rooms even though my walls are connected to each other. I've added a light probe and a lightgrid_sky and it still isn't working.

Try adding a caulk shadow on that wall on the outside that covers it. Should fix it after a lighting rebuild

I tried that and its still showing the light.

If you place the wall a little bit to the right, it will be gone xD

Is the reflection_probe area touching all sides of the room? I had this problem, and setting up my probes correctly fixed it.
Watch this video for more on that: