Dishwasher not removing tea stains from cups?

Our dishwasher always cleaned all the tea stains off of cups. It suddendly started leaving the stains untouched, on checking we found it had moved and was no longer level. We repositioned it securely and made sure it was level. We cleaned out all filters and run a dishwasher cleaner through the machine, checked both arms for blockages or splits, both 100% ok. The machine still doesn't quite remove all the stains, much, much better than before but not as good as before the problem started - any ideas?