What happened to my room acoustics

First of all, your listening position need to be 5 feet closer. Things are actually worse then they seem. The Y axis is in 20 dB increments. Most systems I have seen use 5 dB increments. This is a very shouty curve with the bass lagging 10 to 15 dB behind the midrange. From 200 Hz up things are actually quite good except for that dip at 12KHz. You need to measure each channel separately and compare. 

The ideal in room curve starting at 20 Hz which should be 5 to 10 dB above baseline sloping down and reaching baseline at 100 to 120 Hz, then flat out to 1 kHz then a steady slope downwards to 6 to 12 dB under baseline at 20 kHz. Bothe channels should mirror each other directly. I would like to see if that 12 kHz dip is in both channels. Any difference between the two channels will screw up your imaging. 

You need to deaden the front and side walls at the first reflection point which may calm your midrange and I would remove the bass traps. After that your best option is a digital preamp with EQ and room control. Subwoofers and digital bass management would give you much more control over the bass. 

Don't feel bad. I have measured many systems worse than this. I just measured a system with Magico S7 loudspeakers. The imaging was pitiful for speakers of that caliber. Low and behold one channel had a 10 dB dip centered on 300 Hz. He is ordering a DEQX Pre 4 which will fix the problem. This is like a photograph out of focus. You use digital EQ to focus the system and you can see the results with your measurement system.  

Your room doesn't look that bad to me, many are much worse. Of interest is that you mapped out the "golden triangle" and then didn't adhere to it. As others have suggested, your listening chair is too far away from your speakers. I suggest you pull your speakers another foot into the room and move your seating position at least two feet farther into the room. Try listening to music instead of measurements.

A few comments:

Yes, move the seat forward. You’re probably hearing a lot from the rear wall you could eliminate by moving forward. My speakers are 8 feet apart and I sit 10 feet away. My back wall is another 9 feet behind me. Worth a try.

Did I miss comments about ceiling height? Some of the worst reflections come from floor or ceiling. They may be interfering. It's very helpful to measure impulse responses to see how the reflections are, or you won’t get a handle on imaging and soundstage.

Get those as many reflections between 4 and 12 ms down below -20db if you can. Viz.

- There is a roll-off before 20kHz.
- A dip is present around 12kHz.

COMMENT: These are very high and likely won’t matter much. (In my view.)
- There is a noticeable boost between 50Hz and 1.5kHz.

COMMENT: Much more important.

@lanx0003 

I agree with others, your listening spot is too far back. If your speakers are 9’ apart, try moving your listening spot to 8’-10’ a few inches at a time.

All the best.

In my opinion:

 "There is a roll-off before 20kHz.."  This is the shortest wavelengths being absorbed by surfaces in the room. 

"A dip is present around 12kHz.."  There will be a on-axis cancellation dip in the response with a round horn or round waveguide, centered on the frequency where the mouth reflection arrives 180 degrees out-of-phase a the listening position.   The center frequency of this dip changes with listening distance or microphone distance.  Off-axis the arrival time of the horn mouth reflection is smeared, and the cancellation dippage is correspondingly reduced. 

"There is a noticeable boost between 50Hz and 1.5kHz."  The midwoofer's pattern is wider than the waveguide's pattern below the crossover frequency resulting in more in-room energy below the crossover frequency.

Duke