One of my DC( Win 2012) , DNS seems to be corrupted as it is not showing SRV records for one DC.

Any option is there if  I can rebuild the DNS alone without demoting DC?

Check this article it will show you how to rebuild your DNS

http://support.microsoft.com/kb/294328

But before you do that take a look at an ealier post from someone who also had problems with SRV record:

http://social.technet.microsoft.com/Forums/windowsserver/en-US/23537428-6e5b-468e-b9e4-1acd58d88196/dns-dc-a-records-and-srv-not-completely-up-to-date?forum=winserverNIS

Hope this helps you out.