Raid1 drives fail

I have 20 G-Tech drives for my Mac. 4 of these are configured as Raid1. In the last 2 months 3 drives have displayed a RED FLASHING LED. I went through the REBUILD PROCESS - a 12TB drive took 2 days. Now the 4th one has displayed a RED FLASHING LIGHT. That is 100% failure. As previously I first copied everything off the drive then a strange think happened - the RED LIGHT CHANGED to the WHITE LIGHT – do I go through the rebuild process?