Here I did a curve with just mains, no subs and bit more smoothing at 1/12.
Look closely at phase between mains and subs. If you don’t have the phase right, it cuts out a hole where they should overlap due to cancellation. This same issue plagued me for a while, and while phase may not be the total solution, it’s a strong cause of “where’s the bass?” I found the lowest bass was dependent on the placement more, while the frequencies near the x-over point were very sensitive to phase.
Here is another comparison, this time with left sub, 2 subs and no subs and a bit more smoothing (1/12) to make this more clear.
Great pic. Um, you definitely have complications. There's an increasing trend from 60 Hz to 1 kHz. This should be flat or descending. Also, notice the regular ripple starting at around 6 kHz. That indicates regular reflections in the mid-treble.
Essentially you have way too much mid bass to mid energy. If this is a highly reflective room that would explain it. Before adding the sub, fix up your mains and room.