ADD SELLERS IN FILED 26QB

Dont worry, You can file revised return 26QB.

You should have deducted TDS @ 1% from seller or less this amount from your payment. If you had done correctly. Then, no need to worry. File revised return and correct your mistake.

Before, the financial year is completed.

Filing Revised TDS Return Online: Step-by-Step Guide

https://blog.saginfotech.com/correct-form-26qb-online-traces#

Let me know what have you done? 

What is the purchase price?

How much did you deduct?

What are the consideration of each seller?