Hello,
There should not be an issues with reporting of latest SEP 12.1.4 clients to the older version of SEPM 12.1.3
However, I would recommend you to install the Latest version of 12.1.4 on SEPM as well.
For this to happen, you would have to import the latest packages of SEP 12.1.4 to the SEPM 12.1.3
Download the Symantec_Endpoint_Protection_12.1.4_Part1_Installation_EN.exe and extract the files. Later follow the steps provided in the article below:
How to manually import client packages into Endpoint Protection Manager (SEPM)
http://www.symantec.com/docs/TECH122824
Hope that helps!!