Thanks to everybody for input and suggestions!
I did two experiments last night. One, as proposed by mjbphotos, bringing the panels inside the booth and enclosing them around myself while the booth remained in the corner. That actually had very little effect. The muddiness and pronounced...
After nearly three months of research, experimentation/troubleshooting, and a bunch of expenditure, I have arrived at a brick wall in a quest to get the equipment & environment correct for decent voice over recording. I am hoping the sages here can point me in the right direction before I spend...