For me i used Suntek HP20, it is on all the windows, so also the back. You also see it when looking from the inside and i tinted it myself (it's my friends car). It is only 3 days ago tho so maybe it will go away? I don't know
I have the exact same issue! I can't find anything about it online. I can only find information about tint being 'blurry' the first two weeks of installation but i don't think they're talking about this and have never had this before