I'm not sure this applies to you but...
Yesterday, I noticed my se846 lost all is bass and oomph.
After playing with them a bit, I realized the nozzle and collar had become loose. I had to tighten it and ensure there was no space between the collar and shell and that it was properly seated. There's a specific way to put the nozzle in first. I learned this after closely following the instructions in the manual.
After doing this, they sound like heaven again. I almost lost my mind when they didn't sound good!