Reviews being marked unhelpful

Hi I have been noticing for some time, my reviews have been getting marked unhelpful almost immediately by what very much looks to be a malicious user. Just a few days ago they hit the 25 most recent ones with unhelpful! It seems to have been going on for some time, I would greatly appreciate if it could be checked out. https://www.imdb.com/user/ur1616919/reviews/?ref_=up_ururv_sm Thanks :)