Suspicious Downvoting

I regularly review UK comedies and dramas as they come out. I have noticed in the last few months that within a day or two or posting all of my reviews are downvoted in a straight sequence of 10-12 in a matter of minutes that is completely at odds with the spilt of the previous votes, often taking me from a highly rated review to a bottom rated review against the flow of simlarly rated reviews. e.g. my review is 7/10 and matches the other top ratings and suddenly ends up bottom...

Is it possible someone with multiple accounts is doing this as they disagree with my perspective. Is there a system to detect spurious voting to manipulate reviews?