have a try with more space to the backwall, more space between the baffles and baffles fully parallel. Additional you can dampen the rear- wall a little and put a carpet on the floor between baffles and listening- position, also you can use one small self- adhesive felt- pads 90 degrees and around 10 cm out of the corner on every wall for damping echoes in the upper midrange(so you get three in every corner). Are the woofers running (i remember in your last post you had only the baffles running)?
Regards
Robert