Atmos null at 1270 khz on audyssey editor app

"...Are these reflections off the ceiling itself interfering with the direct sound?..."

Sounds like a reasonable theory.   

Russ. I'm not sure. I have a drop ceiling and the speakers are installed in the grids that way. I measure using the auddesey app and the included mic on a tripod.  I just find it strange all 4 have the same type of reading. My other speakers do not show this null at all. Is this just the way atmos channels measure? Are these reflections off the ceiling itself interfering with the direct sound?

That sounds like a room issue or a measurement equipment issue. It's hard to boost a null.