My dishwasher which uses finish lemon powder is not removing tea stains from inside white mugs. Only recently noticed whilst everything is cleaned very well there is something amiss. I use finish salt and rinse aid and these are correctly dosed and measured as per the book. If I put the cup in the sink with a splash of bleach it goes back to white again. I thought the powders had the bleach in it. On the box it says it has oxygen based bleaching agents. What does this mean or is there a fault. As I say it’s cleaning very well apart from this issue.