This is a myth about price drop because of bounty hunters) IMHO most ICO just too late with exchanges and roadmaps. So people tired from them and selling everything. Or promised great exchange and after that you can see them just on IDEX) Or for example look at fusion on bitfinex) They have no volume at all) And their price is not because of bounty hunters)
Are you a bounty hunter?
Anyway - there can be many reasons. Right now the major reason is the market situation. There just isn't enough people who want to buy and this driver the prices lower and lower.