Stringbed stiffness is the major matter!
I agree with the other guys, if you change tensions and stringers there are too many factors that may vary.
The difference in feeling does not come from the difference in tension on the machine but in the difference in final string bed stiffness.
If you were happy with 60 lbs before and unhappy with 58 and 55 now the difference in SBS can not be in relation to the difference in tensions. These stringers must have lost more tension that your old guy.
My advise is to find a player, shop or stringer who has a stringbed tester and find out what your stiffness is.
If you want control you need to be at 37 DT (kg/cm) or higher.