PRV - lower volume for just one note(Solved by our resident Guru)

There are several ways to decrease the velocity of one note. One way is to select the note on the PRV keyboard. Then move the mouse over one of the notes selected in the PRV. When the cursor changes to a pencil with velocity bars to the right, left click and drag down. A popup will indicate the change in velocity.

Click the keyboard or note name at the left to select all of the events on that note number. Then hover your mouse over one of the notes until you see the velocity tool icon (looks like a histogram), and click and drag down to lower all the velocities by the same amount.
 
Depending on what drum synth you're using, you can also just lower the volume for that piece in the drum synth's mixer.