1. Reset any EQ settings that may be configured.
This includes any settings in the Melomania Connect App, for the device itself and the app used to play audio. EQ settings may alter the sound of your headphones.
2. Try playing from a different source device and app to see whether there is any difference.
3. Perform a factory reset on the P100.
You can perform a reset on the headphones by following the steps here.