It could possibly be related, but no one can say for certain. Downvoting is anonymous by design.
The thing is, when you post a series of bad or low-quality questions on one site, that's a sign to experienced users that you've probably posted bad questions on other sites. People often go and look at your recent questions, and if they find that their theory is correct, they'll downvote. On the other hand, if their theory is incorrect and you've actually asked good questions, you can benefit from this behavior as they'll generally upvote your questions or even answer them!
Ironically, asking this question calls even more attention to your questions and increases the chances people will look at them. Users who read your question here will wonder if those downvotes are legitimate, and check out your recent questions for themselves.
The same rules still apply, though, no matter how old the questions are. Good questions get upvotes; bad (or poorly-asked) questions get downvotes. If you're worried about the votes you're receiving on old questions, that might be a sign you should revisit those questions to edit and improve them.
If the downvotes are truly malicious (e.g., someone is out to get you), we have a script that runs automatically about every day to reverse these votes. You'll find more information here.