Hi dannylibs,
While it’s not really possible to “diagnose” mattress comfort or alignment issues on a forum because there are too many unknowns and variables and individual circumstances (or in some cases health issues) involved that can affect how each person sleeps on a mattress in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) 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.
Having said that … the most common reasons for lower back pain is a mattress that is too soft or from sleeping on a mattress that has developed soft spots or impressions in the mattress or from a support system that is sagging underneath it.
Phoenix