Hi coast,
Thanks for the picture … I appreciate it
Unfortunately these types of issues (foam softening and breakdown leading to the loss of comfort and support that isn’t covered by a warranty) is all too common with these types of mattresses. The old Sealy Springfree mattresses have now been replaced by the Stearns & Foster Luxury Latex line but they have the same issues and most of them (in both lines) that are softer than the Brasswood use even thicker layers of lower quality foams above the latex.
I agree … and these mattresses are a good candidate for mattress surgery (see post #2 here) … especially since you’ve already taken the first step!
Replacing the lower quality layers with a layer of higher quality material (such as latex) in the right firmness level and thickness will give you a better quality mattress than when they were new except you won’t be able to finish the seams quite as nicely without specialized tape edge equipment.
Phoenix