A 50Hz suck-out seems to be a typical issue in a lot of rooms. I've seen some report dips as much as -20dB!
You can't fix a suck-out (null, dip, etc, etc) with DSP or EQ. The only thing you can do is tweak either loudspeaker/subwoofer position, listening position, or both. Attempting to use DSP or EQ by adding 10+dB boost will do nothing but drive your gear, amps and drivers into clipping and distortion, and unnecessary stress as well as possible damage.
Other options are treating the room with more bass traps (all four corners from floor to ceiling if you can), or using more subwoofers located elsewhere in the room.
And yes, as far as your dipole subs are concerned, you need to have them pulled at least 3' from the front wall, if not more.