So the Solo and Dim buttons in the Mix Module are not lit?
Do all your other tracks go through some bus that the Drums bus doesn't? If so you should check that bus for Prochannel EQ or other FX/Gain changes that might have dropped the level.
Are the other tracks pure audio, synths or a both? What else is in the project?
Have you bounced any part of the project to another track that might have phase inverted and be partially nulling the live tracks?