Terraform Upgrade 0.14 to 1.1.9 showing addition in resource without change in configuration

Question

Terraform was working on version 0.14.11 since long. That is been upgraded to v1.1.9 without changing any configuration. Yet in terraform plan it is showing that certain argument will be added.

For example in aws_dbinstance, no configuration is changed and also argument like character_set_name, domain etc.(Marked as Bold) are not defined in resource yet in plan those values are getting showed as addition.

~ resource "aws_db_instance" "test" {
    **+ character_set_name                    = ""
    + domain                                = ""
    + domain_iam_role_name                  = ""**
      id                                    = "test"
    **+ identifier_prefix                     = ""**
      name                                  = "test"
    **+ nchar_character_set_name              = ""**
    # Warning: this attribute value will be marked as sensitive and will not
    # display in UI output after applying this change. The value is unchanged.
    ~ password                              = (sensitive value)
    **+ performance_insights_kms_key_id       = ""
    + replica_mode                          = ""
    + replicate_source_db                   = ""**
      tags                                  = {
      "Name"        = "test"
      "environment" = "test"
      "product"     = "test"
      }
   **+ timezone                              = ""**
  }

Is there any clue on this behavior ?