El Capitan's Disk Utility won't format new 3 TB drives higher than 800 GB
Your problem is probably related to the 2.2 TB (or 2 TiB) limit. Your disks either have an MBR (instead of a PMBR) or it's a limitation of the firmware of the kdLinks HDD disk station.

Check the disks after getting their disk identifiers with disktuil list with sudo gpt -r show diskX with diskX the disk identifiers of the external disks (e.g. disk1 and disk2).

If you get an output like this:

gpt show: /dev/disk1: Suspicious MBR at sector 0
      start       size  index  contents
          0          1         MBR
          1          1         Pri GPT header
          2         32         Pri GPT table
         34          6
         40     409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
     .....


destroy the MBRs and add a proper GUID partition table.

To destroy the MBR and restore a proper GUID pt use:

diskutil umountDisk diskX
sudo dd if=/dev/zero of=/dev/diskX bs=512 count=1


Destroy the GUID partition table and create a new one:

diskutil umountDisk diskX
sudo gpt destroy diskX
sudo gpt create -f diskX


with diskX: once more the disk identifiers of your external disks.

Be sure to use the proper diskX or you may accidentally delete valid disks!



After removing the MBR you often/sometimes have to completely eject the drive (or reboot your Mac) for the changes to take effect.



Update:

With your partition data posted one can definitely say it's a 2 TiB problem:

The default size of the disk is 5,860,533,168 blocks. Your gpt output shows a size of 1,565,565,872 blocks. The difference is exactly 4,294,967,296 blocks which are 232 blocks or 2 TiB.