You may expect a DLF of 1.2 for the 4th mode shape/frequency pair. But each mode holds only a portion of the total system mass. The 4th mode does not account for all the mass activated by your event. The modal response to the applied load is also affected by the location of this load. (The response to the same tap on a water glass changes based on where you tap the glass.)
Take a look at the participation factor for your 4th mode. If you change the DLF associated with that frequency, you will see a proportional change to the participation factor.