Inequal volume

In the piano part of a score of mine, any note above C5 is played very quietly, I've tried using marcato's or accents to compensate but i cant get it to sound like every other note. I've tried using an individual dynamic on every note so that notes below C5 are all mF and all notes above are FFF (any dynamic above FFF just sounds like mF) but it still doesn't equalize the volume, the only way is to make the notes above C5 FFF and the lower ones PP, but then the whole line sounds much to quiet.

This is only a problem when playing the music, if i click on the notes they all have the same volume regardless of pitch.