Solr Cloud leader propagates slow to other nodes

[Cool Techi]

Hi,
We are using solr  4.8.1 cloud and have a single shard core and 3 replicas in 
total.  We are noticing the following issues,
1) Master propagates slow to to the other nodes/replicas.2) This increase over 
a period of time, i.e the data propagation time increase as the time from which 
leader is elected increases? 
What could be causing this, our commit settings are given below.
 <autoCommit> 
       <maxTime>12000</maxTime> 
       <maxDocs>25000</maxDocs>
       <openSearcher>false</openSearcher> 
     </autoCommit>

    <!-- softAutoCommit is like autoCommit except it causes a
         'soft' commit which only ensures that changes are visible
         but does not ensure that data is synced to disk.  This is
         faster and more near-realtime friendly than a hard commit.
      -->
       <autoSoftCommit> 
         <maxTime>1000</maxTime> 
       </autoSoftCommit>
Regards,Ayush