I received a Merkur 38c only yesterday and have used it only once. When i picked it up today 24hrs later i have noticed that the blade guides have turned black on one side as if they have been oxidised. I have attempted to remove this using toothpaste and then tried the aluminium foil baking soda in boiling water. Neither have worked. Anybody got any ideas as i only want to send it back as a last resort.