Return Advice

I bought a NWT dress and when I received it, it had stains on the hem and under each armpit that you can’t see in the listing photos. Seller responded to my return request (as expected) that they inspected the item and it wasn’t this way when shipped out. However, when I went back and looked at the listing photos, I can faintly see one of the stains, since I now know where to look. If you don’t know what it is, it kind of just looks like lighting.

Should I respond? Or does this just go in their favor that you can subtly see one of the stains? Should I just let Posh sort it out?