Happened to me too. I killed the slavers first and then handed in the quests. Went to do this one and after handing over the head/telling her I killed them, I told the leader the plans for Crookspur Island and she cut off there and didn't update the journal at all. I tried to talk to the queen after and that did not work. Luckily I have a save but it means I'll have to go back an hour, as I made it before killing all the slavers.