Unplugged softener affecting pressure
If the system is in bypass then the plug is some place other than the softener.
Where is a good question and with out seeing what the lay out is, or if there is another filter in there that has pluged up...
If there is a pressure tank, there is an out side chance that it is water logged and part of the low pressure.
What part of the country are you in and what was the water test, ie iron hardness ph ...