How to resolve GTID difference between Master and Slave servers in MariaDB replication using MaxScale?

I wrote accidently directly on the Slave DB, and therefore the data is not in sync anymore. When I check MaxScale status, all servers are running, but the Slaves are not detected as "Slave" and there is a difference in GTID. Does anyone know how to put them back in sync? I've already searched for information into the documentation of MaxScale, but I could not find this specific usecase there: https://mariadb.com/kb/en/mariadb-maxscale-2302-automatic-failover-with-mariadb-monitor/