Hi Polleus,
Unfortunately, it’s not possible for me to make any sort of an accurate “diagnosis” of what might be causing your issues, as there are too many unique unknowns, variables and complexities involved. Post #2 here does have some good general information about what commonly is the cause of specific back pains that may be worth reading.
Sudden changes like what you’ve described “tend” to be environmentally (job, stress, flexibility, recreation, strength…) related, as opposed to the mattress, as the mattress wouldn’t have a dramatic change within a few days. Are you able to coincide this change to anything that may have happened to you (sudden twist/turn, physical exertion…)?
If you don’t think this pain is the result or being exacerbated by something that happened outside of the “mattress environment”, it could be that the upper comfort layers in this mattress are a bit too plush for you. As you have the level 8 plushness (24/19 ILD layers), you may wish to experiment and rearrange the latex layers so that the 24 ILD is on top and the19 ILD is beneath that and see if you notice an improvement.
I remember there was a physical therapist whoposted on the site a few years ago, and she specifically referenced side rib pain, noting that side rib cage pain in the morning is usually an alignment issue (of course this is all general information), and as your mattress does use a very supportive polyfoam base, it could be that with your plush configuration that your “comfort cradle” is a bit too deep for your personal preference.
I would also strongly recommend a phone call with Dreamfoam and acquire their opinion of your situation, as they will be in the best position to make a recommendation based upon their knowledge of their product and the detailed information that you are able to provide to them.
Phoenix