Plate Amp 2.1 very high gain for stereo channels


I have just finished my speaker with the 2.1 plate but have a bit of issue with the levels.
My mono speaker is 88db / 2.83v and stereo speakers 90db / 2.83v both are 4 ohms and from the same brand.

So i would assume that i needed to lower the pregain of my stereo speakers around 5db to keep them in level. However i need to lower them 17db to keep everything in line. This is verified both by ear and from measuring the speaker.

The stereo speakers also sound somewhat distorted.

Is anyone else having similar issues?