PostgreSQL streaming replication with slots works for one slave, but not for another slave

Master (10.0.0.1):

Edit postgresql.conf

listen_addresses = '*'
wal_level = logical
max_wal_senders = 3
max_replication_slots = 3
hot_standby = on

Edit pg_hba.conf

host    replication     postgres    0.0.0.0/0   trust

Create a replication slot for the slave

select * from pg_create_physical_replication_slot('master');

Slave #1 (10.0.0.2):

Remove 9.4/main directory

rm -rf /var/lib/postgresql/9.4/main

Do a base backup of the master

pg_basebackup -P -R -X stream -c fast -h 10.0.0.1 -U postgres -D /var/lib/postgresql/9.4/main

Edit recovery.conf

standby_mode = 'on'
primary_conninfo = 'user=postgres host=10.0.0.1 sslmode=prefer sslcompression=1 krbsrvname=postgres'
primary_slot_name = 'master'

Copy conf files from master

rsync -av user@10.0.0.1:/etc/postgresql/ /etc/postgresql/

Restart cluster

pg_ctlcluster 9.4 main restart

Slave #2 (10.0.0.3):

Same steps as for slave #1 except the ip of the slave is different.

The problem: A change on the master propagates the change onto slave #1 but not slave #2. Tried rebooting slave #2 and setting up again from a fresh install but still doesn't work. Any ideas?

Thanks!