If I could turn back time, avoid lower end Gigabytes GPUs.
Yep, I'm in the exact same boat. We don't have nearly as big of a farm as you operation, but out of almost 100 GPUs, the only ones we have had issues with have been Gigabyte "Windforce" models.... the coolers are not very good at cooling and the fans die much faster then any other models we have. In fact, in the past <18 months all of our cooler/fan failures have been from them except one Asus Strix 480 that has a sticky fan (one out of 3 fans on it, so it still cools very well).
+1 for this especialy windforce models,have bunch of 1080s and and on almoust all of them at least 1 fan is having a problem/making to much noise.Some of them started having problems in less then a month after getting them,aorus on the other hand are working fine so far