Yes, use a toothbrush and some alcohol (in Australia it is called methylated spirits). You not only want to clean the grill but dissolve any wax build up or grime. (just dip the toothbrush in a cap of alcohol to wet it)
I'm guessing it is the problem especially if it just went like this from a normally working earphone.
its called methylated spirit everywhere for simple reason that people don't consume it............as methyl alcohal is a poison basically