Wells can change, some times in weeks other times over months.
Any number of reasons for the change, more water use in the area by other new homes.
There could have been an Earth Quake that has changed the ground formation some place that feeds your water table.
There could have been a large run off or a lack of a run off that is now effecting your water table...
Some thing to try for now to see how it works is to set the hardness setting to 53 or just above and cycle the system a few times back to back.