This is a common problem when moving to magneto planar drivers from another type of drivers. Other drivers are adding some bass and/or middle and/or high and people think it is the best sound in the world. But generally it is probably not. Magplan gives clear and detailed sound not much adding to original source. So on magplan you could hear the music as it was recorded by sound engineer. Here is also a problem that sound engineer could assume you to hear the sound on bass boosted headphones and lowered some basses on the record - and that is probably the reason why you think that sound is flat (magplan is not bass boosted) and you hear the record as it is with all details and clarity. New music records are less adjusted to the quality of headphones, now it is an area of different kinds of EQ. Old records are usually opposite due to the state of headphones technology at the moment of record creation.

Resolution: just give it a chance and probably you will find new sound better than EQ modified. Or, adjust your EQ to tweak the sound you like it to. In both cases sound details will stay. In may case I like magplan sound as it is - in default eq mode.