Can the goals in a goal plan be updated after plan has been assigned to employees?

We currently have a goal plan with the below setup:
- 8 goals in the goal plan - 5 performance goals and 3 "special" goals
- 5 performance goals are weighted at 8% each (in the goal plan, these are generic goals titled Goal 1, Goal 2, etc., that the employee/manager update - all fields except goal category and weighting are editable)
- 3 special goals are weighted at 20% each (in the goal plan, these are titled Special Goal 1, etc., and only the success criteria and notes fields are editable)
- Goal plan is limited to these 8 goals and assigned to all employees
- Goal weights are enabled and sum of weights must be 100%