Hopefully someone more knowledgeable like Craig will jump in but I think you may want to re-run XT32 after adding more bass traps to the room. Here’s my overly simple, probably wrong,
thinking on it but here it is anyways.
Prior to your current treatments and Audyssey XT32, you may have had a Bump/boost (8 db) at say 100hz and a dip (8db) at say 160hz, then a dip again at 220hz and etc (not saying that’s the case - just shooting out random Hz and random decibels reading). After adding your current treatments, it could have reduced that Bump at 100hz by 4db and could have raised those dips by 3db (again random numbers). Running XT32 should have taken all of this into consideration and gave a flat or flatter response (which is what you currently have).
Adding new 4 inch thick bass traps to the side of the speakers may actually help with side wall reflections but it may also resolve some bumps and dips you had prior
to Audyssey XT32. So by adding more traps now and Not re-running Audyssey, its theoretically possible that you could have dips in places where you previously had a boost and a boost where you previously had dips. This leads me to believe that running Audyssey again after you install the new bass traps/treatments would be a good idea.
I’m not sure if I clearly stated it above so I’ll try with the examples below:
Step 1: 100hz +8db
and 160hz -8db
Before Treatments and prior to Audyssey.
Step 2: 100hz +4db
and 160hz -5db
After your current Treatments only.(dips and boost reduced)
Step 3: 100hz 0.0db
and 160hz 0.0db
Audyssey XT32 and current Room Treatments (flat response)
Step 4: 100hz -3db
and 160hz +3db
New Side Bass Traps next to main speakers & not re-running X32.
Step 5: 100hz 0.0db
and 160hz 0.0db
All Treatments and Re-running Audyssey XT32 (flat response)
This is all theoretical of course and an over simplification. It seems to me that re-running Audyssey, while not "necessary" since (Step 4) is still a really good/flat response, would only help.