G-RAID TB2 8TB Drive upgrade issue

Hi, I replaced the 2 x 4TB disks in my G-RAID for 2 x 8TB Seagate Barracuda Pros several months ago. Since then, I have experienced very slow mounting and when the Raid is powered on, it spins up momentarily then cuts out. It does this a few times then eventually mounts after around 30 mins of unplugging/powering off/on.

Today, it hasn’t mounted at all and the top drive has no activity. I put the old drives back in and they work absolutely fine with a fast mount.

Do you think it is a power issue? The new hard drives are drawing more power than the originals? Has anyone experienced this? I could perhaps get a higher amperage 12V power supply?

Thanks in advance!