Where is the problem? Tracking error?

Let say I am listening to a piece of classical music. Full Orchestral. When the strings and everything sounds mushed together especially during loud demanding peaks, what is the likely culprit? cartridge, tonearm, or isolation? During certain passages, is it a tracking problem that some cartridges cannot handle all of the vibrations occurring in the groove and is that being magnified by not enough tracking force, isolation, platter not having enough mommentum? Just curious... I do not notice this when listening to CD's so I know it is not anywhere else. Everything is clear. It has to be occurring on the turntable. Where should I start looking for answers?