Normal to be able to spin valve springs by hand ?

As someone whose job is working on cylinder heads every day.....since 1990.....
I can tell you it’s not that hard to rotate stock springs by hand on most heads.

You’d have to test the springs at their actual installed height to determine if they are in fact out of spec.

As mentioned, there could easily be some seat recession going on which will reduce the spring load.
This is typically most prevalent on the exhaust.
Pulling the rockers and putting a straight edge across the valve tips should help tell you if there are issues in that regard.