It seems to me that you have accepted alot of people, whom only post in bounty campaigns and have a low post quality (without any kind of contribution).
It's not too late too turn around and hire someone who is experienced on this forum to manage this campaign. I've seen many services get their reputation ruined because of horrible campaign managers who accept spammers into their campaigns. DT members are not known to like such behavior.

It's your reputation, and i just wanted to know what you might be facing here.