Adding it behind the diaphragm so it's not touching will affect any potential cavity resonance, but do nothing for any diaphragm breakup itself. If it's touching the back of the diaphragm, then it could easily be having an audible effect, any maybe not for the better (allowing for a response that's a subset of Beranek's Law)
Measurements with a calibrated mic and REW would add to seeing what you actually did. MCACC and their mic paint with a fairly broad brush.
“You are not special. You are not a beautiful and unique snowflake.” Chuck Palahniuk