Version 2.0.4 of Bitzecd includes a fix for the bug described here (https://bitzec.github.io/support/security/announcements/security-announcement-2019-03-19/).
Users should install this update and then rescan the blockchain by invoking bitzecd -rescan. Sprout address balances shown by the bitzecd wallet should then be correct.
Thank you to Alexis Enston for bringing this to our attention.