"What would I have to change to correctly substantiate my TN residency?"
To add a bit to @Hal_Al 's answers, if questioned you'd have to prove to the California FTB that you have changed your domicile to TN. Note that "domicile" and "residence" are not necessarily the same thing. I suggest you read the section Meaning of Domicile on page 10 of this reference, which @Hal_Al previously provided to you:
https://www.ftb.ca.gov/forms/2021/2021-1031-publication.pdf
In particular, read the paragraph under Change of Domicile.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
