I would not bank on Discover pulling TU. It is definitely not guaranteed. A lot depends on your state and sometimes it can vary in the same state. Mine was pulled a few months ago in TX showing up as EX.
This document might help but I would not bank on TU:
https://www.mybanktracker.com/credit-cards/credit-score/credit-report-discover-pull-273444
Credit unions more often than not use a single CRA but not all follow this policy.
edit: congrats on your Prosper loan.
