MySQL multiple GTID Executed GTID set

I believe I have an issue of sorts with MySQL Replication on the slaves. Instead of there being one clean GTID under 'Executed GTID Set' there are multiple GTIDs.

Retrieved_Gtid_Set: 54206435-24c7-11e5-bd59-1458d055bee8:354806-354826
Executed_Gtid_Set: 54206435-24c7-11e5-bd59-1458d055bee8:1-354826, cd975336-24c7-11e5-bd5c-1458d04f9808:1-24

I've tried a slave reset all but this doesn't seem to clear it.

Has anyone seen this before? What might be the best way of resolving this?

Thanks in advance