we've a new rangemaster stove (only two weeks old!) & tonight I carelessly let a pot of water boil dry. The hob has been left with a cloudy haze under the glass. There is nothing to scrub off, it seems to be a discolouration of the glass hob. I fear that it’s a metallic burn in the glass. Could anyone advise me if this is fixable? It looks awful! I’m so annoyed!!