Challenging Room Node

The basic GIK panels wont work well at these frequencies.

You need Soffit traps or Tri Traps.  Stack them up in the corners so they reach up to the ceiling as much as possible.

The professional room solution is often a combination of bass traps + EQ.  See if these traps at least improve the null you are having. If so, and you are using Roon or any other EQ already,you can then use a little EQ to correct. :)

Let me know what you do and what you find.

Erik

Almost all rooms have vertical nodes unless dba. Most often do to untreated ceilings.

If the suckout is narrow enough (in frequency), it will be almost unnoticeable. That’s good news, because (1) 60 Hz is too low for most porous absorbers to be terribly effective, and (2) if it’s a true node, adding more volume via DSP will not be very helpful. So to my way of thinking, if you’ve found the listening and speaker positions that satisfy your ears otherwise, you could consider just living with it.

The other solution would be subs placed differently from your main speakers. That can be effective, but integrating subs optimally is not a simple task, by any measure.

I tried the distributed bass array with very good results. Added two more subs(had two) and moved them around the room while running the test tones and SPL meter until I got most everything at or at least near the same volume. My subs are very randomly located now instead of being next to my main speakers. It's a lot of effort but it works well. I had at total null at 50 to 60 hz.

Yep, that's a difficult frequency - a porous absorber would need to be over 4' thick (1/4 wavelength), even stuffing that into the corners is going to be pretty obtrusive. A sub array would seem to be a good choice if you have the space and wallet.
If you're really intent on treating the room then there are more options. As you're dealing with a narrow frequency band then you may want to look up diaphragmatic absorbers and helmholtz resonators, both of which are more efficient in terms absorption coefficient but have a higher Q (they cover a smaller range of frequencies). Both need tuning to the room so will require a bit of DIY (I've not checked to see if there are any commercial ones available). If you go down this route prepare yourself for quite a bit of trial and error... also grab a copy of the Master Handbook of Acoustics.
I ended up putting in a suspended timber ceiling made up of 1/2" T&G timber, 6" rockwool and a 6" air gap above that... so I lost just over a foot of ceiling height. I had left myself the option of making holes in the timber to create helmholtz resonators but it's good enough without that.