I have had 3 Zagg Glass protectors on my iPhone 6 recently and they have all done this, it was either on the top bottom or sides, had them installed perfectly and I am ocd at Best Buy and Verizon.. Finally just bought a 10$ Tzumi Glass Screen Protector from Walmart and it is perfect no halo, no bubbles on edges! Although I keep looking at the replacement zagg glass sitting in my room that I paid $35 for and its killing me
One thing I found is the halo or "white" on the edges is much more noticeable on the space gray, I apply them to my white Ip6 and you dont see it as much