TX...whats you draw lenght?
It could be a form issue, but without seeing you shoot, its near impossible to be certain.
One thing to always consider when a bareshaft appears weak and trimming the shaft doesn;t show any improvemnet, is that the shaft was stiff to begin with and more trimming increased the dynamic spine to the point, its htting the sight window of you bow, which kicks the nock end of the shaft to the left and gives a false weak reaction....which well may be the case with a 55/75 unless you have a long draw or left the arrow full lenght, before bareshafting.