You can read about how to interpret the spectrogram
here. This link leads to one part of the official REW tutorial. The result I posted was created by Dirac Live 3 automated room correction software. I myself by manually operating REW and EQ cannot achieve this level of "graphic excellence", but I posted it just to give you an idea of what is possible.
My take is that compared to the result created by the software and the "ideal spectrogram" explained in the REW tutorial, the sound energy in your room has a longer decay time, about 100ms longer in the midrange and even longer in the bass. Also, you have several room modes (those deep wide nulls), suggested by both the rise in the Group Delay Line (the black broken-line) and the drop in the frequency response (think of spectrogram as a 3D frequency response graph viewed from above).
Another member tuga fixed the frequency response graph for you. That is a more accurate representation of how your system sound. If you draw a line at 75db, you can see about a +/-5db variation in the bass and mid-range. That is 10dB of ups and downs, meaning one music note could be twice as loud as an adjacent note.
You have applied very, very mild EQ. If you like the sound now, great, leave it like that. If not, try more EQ. Use REW to calculate Parametric EQ and enter them into your Auralic and see whether you like the result. Unlike room treatment installation, EQ is easily reversible so just be bold with it. I also recommend not using the "calculate target from response" in REW but put the line a lot lower than the measured frequency response, so that the PEQ will do more cutting that boosting. Cutting will give your lower SPL than before, so simply dial the volume up in your amp to compensate for that.
For the nulls below 100Hz, multi-sub is a tried-and-true solution. There are many discussions regarding multi-sub in this and other forums, just search it. You can also read about it in the attached PDF.
Here is a
thread where other members post their results. You can compare yours to theirs. Remember, when reading a graph, don't just look at the shape of the curve, you have to read the vertical axis (Y) and horizontal axis (X).
Have fun!