Several minutes after posting a question I received several downvotes on my questions:
It's not a significant amount of reputation lost but I find it suspicious.
Someone probably read your question and then followed your profile to your other contributions on the site. Why they downvoted is something that's impossible to know unless the voter comes forward. These specific questions have little in common that I can see.
It's disconcerting seeing these many downvotes all at once, certainly. And downvotes without explanations are particularly nasty, but Stack Exchange keeps voting anonymous for what I consider very good privacy reasons.
Since the automagic-fraudbot hasn't picked anything up, I'd suggest just letting this one go for now. If the problem gets worse, you can ask the mods here to bring it to the attention of the SE-folk.