If your action is now really low from just changing strings, your saddles moved during installation. There is no other possible explanation. As for spacing, just think about what you are saying: that the strings are somehow responsible. No. Check your saddles and put them right.
Look if you are going to play bass, you're going to have to learn how the simple physics involved work and learn how to maintain it. Read the setup stickies in this forum and watch " Carl Pedigo's" setup vids on YouTube.
Paying money for others to setup a bass after a simple string change is costly and comes off as laziness because people don't want to spend the couple of hours it takes to learn how to do it. It is so simple. Learn it.
Immigrant says: "Some fuzz be coo', some fuzz be trippin'."