Because the replies are still there. Go delete them and apologize to them with a real reply that adds to their conversation. Actually show them you read their post, they might even take back their down votes if you did that. Since you made those replies and they are still active (7 days posts are active) anyone can downvote them. And all someone has to do is click on your comments like I did to see you have been spamming. If you want to fix it go delete those replies and make new ones telling them you are sorry and actually add something as I have suggested to you already.