Hi darkarchon,
I don’t have enough information to really know with any certainty (I can’t feel what they feel or see them on the mattress and I don’t know anything about their body type or sleeping positions) and what is too firm for one person may be too soft for the next.
If I had to guess though (and it would be a complete shot in the dark) I would guess it was too firm only because I know the mattress is on the firmer end of the spectrum and that the most likely cause of issues for most people would be that it was too firm rather than too soft. Having said that … Mithejj also mentioned that they were used to sleeping on the floor so if they were also in a higher weight range then it’s possible that for them it could also be too soft.
Symptoms that take a longer period of time to feel are most often related to alignment issues (that can be caused by a mattress that is too soft or too firm … both of which can cause different parts of the spine to sag and be out of alignment).
For those who experience various “symptoms” on a mattress it can take some trial and error and detective work to decide how it may need to change (softer or firmer, which layer may need to change, or any of the other changes in design that can help with the feel and performance of a mattress relative to a particular person) but there is much more information about this in post #2 here and the other posts it links to that may be useful and help identify what the symptoms may be pointing to.
Phoenix