Hi mainertodd,
Thanks for the update.
While it’s not possible to “diagnose” mattress comfort issues on a forum with any certainty because they can be very complex and there are too many unique unknowns, variables, and complexities involved that can affect how each person sleeps on a mattress in terms of “comfort”, firmness, and PPP or any “symptoms” they experience … there is more about the most common symptoms that people may experience when they sleep on a mattress and the most likely (although not the only) reasons for them in post #2 here.
You also mentioned in a previous post that you already have back issues so I would keep in mind that even a mattress that is a good “match” for you may not resolve pre existing back issues.
It’s also possible that upper back issues could be connected to your pillow as much as your mattress.
If your back pain is better than it was on your firmer configuration then it could be a pointer that going softer is the right “direction”. If your back pain is worse than it was before then you may be going in the wrong direction by going softer.
Phoenix