A few hours ago I got downvoted on all my questions and only questions. Is it because downvoting question is now free?
Down-votes on questions have been free for a number of weeks now, so it could be that someone's just discovered this.
The vote fraud scripts will detect if one person has voted (either way) on more than N posts in less than T time. I don't know the exact numbers here.
So if that's the case you'll get the points back tomorrow.
If you don't - well just move on. Down-votes happen. If the questions are otherwise OK they'll gain more up-votes in the future.