What causes wierd marks to appear on brand new lenses?

I purchased a new pair of glasses two weeks ago. The first pair of lenses had very apparant marks on them that looked like a chemical had eaten through the AR coating. They remade the lenses and put them in my glasses and everything seemed normal until I got home and saw my lenses in a different light. There is a very faint circle that looks almost etched on each lens. You can not see it while directly looking through the lens, but at an angle you can. I called the place I got them through and they said they would have yet another new pair made, but I’m kind of tired of dealing with this. I paid 150$ for my lenses (pentax diamond clear with AR coating). Does anyone know why they might have these marks? Also, if they have the same marks on the new lenses, should I just ask for a refund? The company has been more than nice to me and they have done so much for me already…