Actually we cant pinpoint the exact time really on when is these whales are selling.We can just feel it by the huge sudden pricedrop in market. So if you feel its the lowest price already then follow your instinct buying it back.
That is it one does not need to follow any whale before buying or selling all you need to do is to follow your instinct and make your decision as it suit you because the cryptocurrency market operate base on individuality which allow you to make your personal decision and act in other not to be left behind.