Active Directory Replication Issues

I'm really sorry to ask support here for this problem. I'm not a windows system admin, because the sys admin left, i need to correct this issue myself.
It seems that my windows server 2008 have a replication issue.
I have one controller domain on my server, and it seems that 2 other servers are for replication.
here is the result of the command repadmin /showrepl:

Repadmin: running command /showrepl against full DC localhost
Premier-Site-par-defaut\MYADSERVER
DSA Options: IS_GC
Site Options: (none)
DSA object GUID: a470cebf-4768-4e25-8818-e8d416357bfd
DSA invocationID: be4c9f09-14d7-4ed8-9cd1-d21774f92e77

==== INBOUND NEIGHBORS ======================================

DC=mydomainname,DC=com
Premier-Site-par-defaut\CORE01 via RPC
DSA object GUID: 17eb944f-6b02-41d3-9bed-c62f8cbf93ce
Last attempt @ 2016-10-05 10:56:13 failed, result 8614 (0x21a6):
The directory service cannot replicate with this server because the
time since the last replication with this server has exceeded the tombstone life
time.
3330 consecutive failure(s).
Last success @ 2016-05-25 10:58:37.
Premier-Site-par-defaut\CORE02 via RPC
DSA object GUID: 6c71fcbd-9162-495b-8713-bc5fb6bd5a8f
Last attempt @ 2016-10-05 10:56:13 failed, result 8614 (0x21a6):
The directory service cannot replicate with this server because the
time since the last replication with this server has exceeded the tombstone life
time.
3331 consecutive failure(s).
Last success @ 2016-05-25 10:58:37.

CN=Configuration,DC=mydomainname,DC=com
Premier-Site-par-defaut\CORE02 via RPC
DSA object GUID: 6c71fcbd-9162-495b-8713-bc5fb6bd5a8f
Last attempt @ 2016-10-05 10:56:13 was successful.
Premier-Site-par-defaut\CORE01 via RPC
DSA object GUID: 17eb944f-6b02-41d3-9bed-c62f8cbf93ce
Last attempt @ 2016-10-05 10:56:13 was successful.

CN=Schema,CN=Configuration,DC=mydomainname,DC=com
Premier-Site-par-defaut\CORE01 via RPC
DSA object GUID: 17eb944f-6b02-41d3-9bed-c62f8cbf93ce
Last attempt @ 2016-10-05 10:56:13 was successful.
Premier-Site-par-defaut\CORE02 via RPC
DSA object GUID: 6c71fcbd-9162-495b-8713-bc5fb6bd5a8f
Last attempt @ 2016-10-05 10:56:13 was successful.

DC=DomainDnsZones,DC=mydomainname,DC=com
Premier-Site-par-defaut\CORE02 via RPC
DSA object GUID: 6c71fcbd-9162-495b-8713-bc5fb6bd5a8f
Last attempt @ 2016-10-05 10:56:13 was successful.
Premier-Site-par-defaut\CORE01 via RPC
DSA object GUID: 17eb944f-6b02-41d3-9bed-c62f8cbf93ce
Last attempt @ 2016-10-05 10:56:13 was successful.

DC=ForestDnsZones,DC=mydomainname,DC=com
Premier-Site-par-defaut\CORE02 via RPC
DSA object GUID: 6c71fcbd-9162-495b-8713-bc5fb6bd5a8f
Last attempt @ 2016-10-05 10:56:13 failed, result 8614 (0x21a6):
The directory service cannot replicate with this server because the
time since the last replication with this server has exceeded the tombstone life
time.
3193 consecutive failure(s).
Last success @ 2016-05-25 10:58:37.
Premier-Site-par-defaut\CORE01 via RPC
DSA object GUID: 17eb944f-6b02-41d3-9bed-c62f8cbf93ce
Last attempt @ 2016-10-05 10:56:13 failed, result 8614 (0x21a6):
The directory service cannot replicate with this server because the
time since the last replication with this server has exceeded the tombstone life
time.
3194 consecutive failure(s).
Last success @ 2016-05-25 10:58:37.

Source: Premier-Site-par-defaut\CORE02
******* 3330 CONSECUTIVE FAILURES since 2016-05-25 10:58:37
Last error: 8614 (0x21a6):
The directory service cannot replicate with this server because the
time since the last replication with this server has exceeded the tombstone life
time.

Source: Premier-Site-par-defaut\CORE01
******* 3329 CONSECUTIVE FAILURES since 2016-05-25 10:58:37
Last error: 8614 (0x21a6):
The directory service cannot replicate with this server because the
time since the last replication with this server has exceeded the tombstone life
time.

Thanks for helping me