In future I suggest you brief before TOD that you intend to descend at the normal descent speed but if turbulence is encountered then you will reduce airspeed, should you anticipate turbulence in descent then start down early, if you can.
Adjusting speed for light turbulence during descent can be a wasted effort as often the level is a thin one with smooth air above and below, just keep a very sharp eye out for abnormal temperature changes of the air you are passing through as this can be the first clue you are going to get of any rough air.