Your taps and plughole will have been polished then given a coat of clear laquer. The laquer is wearing through and surface corrosion is starting up. (This corrosion can in some cases continue to spread under remaining laquer). You need to completely remove all the laquer using the finest steel wool. This will leave a dull finish. Next, use some 'Solvol Autosol' chrome cleaner paste to polish the brass to its original shine. Follow this with a couple of coats of clear polyurathane varnish. (solvent type, not waterbased). 'Solvol Autosol' is usually available in car bits and pieces shops and some hardware stores. It's also available at Lakeland Limited under the name (I think) 'Maas' chrome polish, but at about three times the price. It won't be an easy task. You may want to but replacement items instead. In that case I'd recommend giving the an extra couple of coats of the above varnish before installing them - the shine will last years longer if you do. Good luck!