I love my Pro 600 (KP26M1XPM) and have been using it for years, but I started noticing that a gray residue would come off the flat beater when I wiped it.  Then my hubby accidentally put it in the top rack of the dishwasher and it came out dark gray with a gritty texture!  Is this safe to use?  I cannot find a replacement beater.  Will the 4.8L flat beater fit KP26M1XPM model?  Any help would be appreciated.