To enable replication of those attributes you must modify the property in the AD Schema plugin, shown below.
1. Logon to a DC
2. From the command prompt as administrator run regsvr32 schmmgmt.dll
3. Run mmc.msc from Start > Run and add AD schema
4. Click Attributes, and locate the attribute you wish to replicate to GC's
5. Select the checkbox to "Replicate the Attribute to the Global Catalog"
Repeat the above steps per attribute that is not currently replicating.