How do I stop external HHD's restarting at the same while downloading torrents to a single HDD?

Question

Guys, I am sitting with a problem which started recently whilst downloading torrents from Bittorrent to a external 6 Tb HDD, whilst another two smaller 5Tb drives are used to view and move downloaded files from the 6Tb drive to the smaller ones. The Laptop I am using is a MSI GT80S-6QD-062ZA Titan SLI Core i7 with 16 Gig of Memory

Sometimes all the HDD's which are three units attached to the laptop, they all disconnect at the same time. They all reboot and then bring up a new Explorer screen and then the torrents show it cannot find the HHD where it is downloading to.

It is only when I started using a 3.5" drive which is powered up from an external power source. One would have thought that if it does reboot, it will only do it alone, but all the HDD's restart.

The other two HDD's are portable HHD's and a 5Tb for both and the larger one is a 6Tb drive.

I have rebooted the laptop several time to see if it is a memory or cache problems, but when connected immediately after the reboot, the HDD's start their cycle of restarting again. I closed the browser to ensure it does not tap away the memory as well.

What I have done also, is disconnect the two portable HDD's as well so that only the Laptop and Desktop HHD is connected and running for the torrent downloads, but to no avail as it also keep on restarting after a while. I minimised the amount of torrent to download by just doing a start and not force start, but also restarting. One would wonder if it is the ports that are disconnecting and what would cause it to disconnect?

Help please