If your link builder did that to you, then it's likely they have control over those links. Check the whois of those forums to see if the ownership is located in the same country as the link builder. If so then it's likely under their control. Ask your link builder to remove those links. Don't be surprised if they ask you for money to undo the damage they caused.
If it's not under their control then contact the site owners directly. The process is to contact the source of the links first to have the links taken down.
60% of links from the same source is not good.