We "upgraded" a dozen of our 400 watt metal halide high bay lights in our shop with LED retrofit lamps where you remove the ballast and extend the line voltage to the mogul base lamp socket. After about a year, they are failing, some flicker, all are becoming dim and changing to a yellowish color. I was surprised at this happening, and wondered if others had similar experiences. The lights are fed with 208 volts, and the lamps are rated 120 - 277 volts. I had inquired if the 208 volt supply was appropriate, and my supplier stated that they should operate normally. Any thoughts or experiences to share?