My fairly new (8 months old) Trek FX7.3 hybrid has developed changing problems on the front chainset Until last week it was really smooth but during my 2 commutes this week it has become a right b*gger. Changing up is OK but changing down has become problematic with the chain quite often not moving between the chainrings and finding a sort of 'neutral' for a few pedal revolutions before moving to the next lowest chainring. Any suggestions as to what could be wrong??? Stretched cable? Damaged chain? Lack of lubrication?