Maybe not. The general rule is you may not claim QBI on income for a job where you were once a W2 employee.
Under the regulations issued by the IRS, if you are working for a former employer as a contractor, doing substantially the same work that you did as an employee, you are ineligible for the QBI deduction for 3 years after you stopped being an employee.
I don't think the fact that you formally retired changes that.
Refernce: https://ttlc.intuit.com/community/taxes/discussion/qbi-for-independent-contractor/00/1083355
