We’ve added more issues of a serial and journal title we are retaining for EAST, are we expected to extend our EAST commitment to these newer issues?

No, the EAST retention commitment is only to the issues the library held at the time of agreeing commitment not to any future issues. Any libraries that voluntarily decides to extend the retention commitment to newly acquired issues should follow EAST guidance for updating the holdings statement in their local ILS and PAPR/OCLC.