My bad. By not touching it, I meant stop backwashing it. Many are removing the backwash valve with the Quad DEs since they work so well for so long without doing anything. backwashing a Quad is largely an obsolete thing, in my experience. There really is no upside to backwashing, and there are downsides. The one that comes to mind is too little or too much DE. Both of these conditions will cause your symptoms if they are far enough out.
So Take it apart, clean it completely, add the right amount of DE, and don't even think about doing anything else for at least 6 months, with the exception of watching %PSI growth at a medium RPM.
In summary, hat I'm suggesting is you are smothering your new child! Let em go out and play in the mud!