Tube amp bias adjustment advice

Not sure why my link to pictures disappeared. Here it is again:

https://systems.audiogon.com/systems/6261

So I have no balance adjustment, why am I hearing more from the left speaker than the right when I am seated in the middle?  They are both exactly the same distance from the back wall and at the same angle, within a 1/8 of an inch.

@needfreestuff I am following the instruction from the manufacturer.  I have single point source drivers, Voxativ 9.87.  I am centering myself between the speakers so the distance is the same so I am confused by your statement.  I find myself needing to sit about 2 feet to the right for it to sound balanced.  Both speakers have about 7' to the outside side walls.  

This is a second set of tubes, had the same issue previously so I am thinking it may be room acoustics. 

I will try swapping the speaker cables L to R and see if I notice any change.  

I had a chance to try a few things including different sources and swapping the speaker cables. I must have hearing loss out of my right ear because I noticed no difference. I will buy an SPL and verify but I asked my GF and she said it sounds balanced when seated in the middle.

One more thought, it could still be my room so I will explore that after I do the SPL.

@needfreestuff i hear what you are saying but my room is a large rectangle 25x20 feet. That being said, the spacing from the back wall is more important in my situation. There is 10 feet between the speakers and only 10 inches between my ears. BTW the speakers are 30” from the back wall on the inside and 32” on the outside.
Bigger issue I believe is a large skylight above the left and not one above the right speaker. If I could post a picture it would be much easier but I don’t see an option in Audiogon

https://systems.audiogon.com/systems/6261 @imhififan thanks for the advice. The first 3 pictures show my room. Please notice the large opening above the left speaker. Anyone know if the room could be causing my problem?