I agree with them. Sounds like you may be some honest and responsible renters. Most renters would leave and either claim it was preexisting from another renter or that finger nail polish remover is commonly used around a vanity and it is expected normal wear and tear that maybe the owner should have considered when they put it in cause nothing lasts forever. There are many different types of countertop materials and they don't all work the best and have certain drawbacks under all uses and circumstances. Normal wear and tear goes with the rent as many products, like carpet, etc. have a life and then need replacement.