Hello,
In your case, it is important to check if these clients are communicating with the SEPM server properly?
Here are few articles which would assist you -
1) Symantec Endpoint Protection Manager 12.1 Communication Troubleshooting
http://www.symantec.com/docs/TECH160964
2) Troubleshooting communication problems between the management server and the client
http://www.symantec.com/docs/HOWTO55017
3) Symantec Endpoint Protection: LiveUpdate Troubleshooting Flowchart
http://www.symantec.com/docs/TECH95790
Again in reference to the MAC clients, I agree with pete...From SEP 12.1, you could deploy the MAC clients from the SEPM. Check this Articles below:
About deploying Mac client installation packages
http://www.symantec.com/docs/HOWTO26788
Deploying clients using a Web link and email
http://www.symantec.com/docs/HOWTO55064
Exporting Symantec Endpoint Protection client installation packages for Mac computers
http://www.symantec.com/docs/HOWTO26789
Hope that helps!!