We emptied our van (nearly a year old) for service. A couple of days later I noticed two spots on the mattress cover, which is usually covered with the duvets. They were like fly dots but as if they'd had water on them so they were blurred - about 2mm across each. The van went for service - 24 hours from dropping and collecting and when we got home there were more of these blurred spots. Definitely not mould. Any ideas ? My first are a resident spider under the bed who nightly poos on our mattress !!!