Wal files being delayed - Pgsql 9.2

Hi guys,

My current scenario is:

master01 - Postgres 9.2 master DB
slave01 - Postgres 9.2 streaming replication + wal_files slave server for
read-only queries
slave02 - Postgres 9.2 streaming replication + wal_files slave server @ AWS

master01 sends wal_files to both slaves via ssh.

*On the master:*

select * from pg_current_xlog_location();

pg_current_xlog_location

--------------------------

1A7C/14AEB2C0

(1 row)

*On the slaves:*

ls -ltr /var/lib/pgsql/archive/

-rw------- 1 postgres postgres 16777216 Nov 14 01:21
0000000200001A7A000000F9

As you can see, the last wal_files on the slaves isn't the
0000000200001A7C* ones. I think the SSH delivery is being delayed. Not sure
why tho.
How can I see how many files are behind?

Cheers
Patrick.