You'll be pleased(*) to know that I just ran a report on downvoting patterns in the last three months and the results show that you have been a favorite downvote recipient of about seven different monks.

One most recent node of yours matching your description is Re: PERL csv files to Excel. And the first vote on it (which was, yes, a downvote) occurred 8 minutes later. Hardly "immediately".

In any case, I don't find any evidence of automated downvoting.