Hi crl2,
They could probably confirm the layering for you but their mattress could be similar to the version 2 mattresses (with one layer on the bottom and one on the top) except they use Celsion (now called Talalay GL or Active Fusion by PLB) on the top instead of the regular Talalay. Regardless of the specific construction though … the issue would still need to be resolved.
Latex is the most durable of all foam materials but softer latex (or any foam material) will be less durable than firmer latex (or a firmer version of any material) and the topper you have is at the very bottom end of the softness scale. There are many factors involved in the durability of a mattress (see post #4 here).
In addition to this … durability is relative to the person because even relatively small amounts of foam softening can lead to the loss of “enough” comfort or support that would take some people “over the edge” if the mattress was “on the edge” of being too thick or soft for you in the comfort layers when you first purchased it (see post #2 here) even if it would still be fine for someone with a different body type or sleeping position where their original choice was more in the middle of the range of comfort and support that was “neutral” or more suitable for them. Your husband is also a little larger so his side may be softening a little more under some parts of his body which could change the symptoms for you when you rotate the topper.
There are also other possibilities that could lead to changes in how you sleep on a mattress including changes in the person themselves, sleeping positions, or changes in other parts of your sleeping system (such as a foundation, mattress pads, pillows, or anything else that is between you and the floor).
As you already suspected … upper body and neck issues are often connected to a pillow and the alignment of the head and neck. Lower back issues are often connected to a mattress where your pelvis is sinking in too far relative to the rest of your body and affecting the alignment of the lumbar. Rotational alignment is also just as important though and if you are out of rotational alignment (the spine is twisting) it can also take some time to develop “symptoms” (just like some things are OK in the short term but can cause “symptoms” if they are repeated over the longer term). From your description and the fact that you are a side sleeper it seems that your sleeping position may be “rotating” your lower body which can also lead to stress on the lower back which can develop over time. I would probably experiment with a fairly thick pillow under your upper leg to lift it up to see if that helps with the rotational alignment issues that may be causing your “symptoms”.
It’s also possible that you may need a slightly firmer topper which may reduce the amount your upper leg is sinking into the mattress and twisting the spine (if that turns out to be the cause) but I would start with trying a pillow under your knee.
Phoenix