Specialized Stain Identification and Removal Service/Kit for Bathtubs

The user is distressed by a dark stain appearing in their bathtub after bleaching and scrubbing, indicating a persistent and perplexing problem not solved by standard cleaning methods. This suggests a need for a specialized service or product that can diagnose and effectively remove unusual or deeply set bathtub stains that resist common household cleaners. A kit could include targeted removers and tools, while a service could offer expert assessment and treatment for such stubborn issues.