Went to the Isle of Wight for a couple of days. When I got home my slippers had some sea weed on them(big mistake not to wash them before that). So they fell out of the bag and me not noticing the weeds right away - they lay there for a day. Long story short - the carpet has greenish stains on it. I tried to wash them with a carpet shampoo but they are still visible. Any advice on cleaning it?