- when you have a number of different posts (answers or questions, old or new) all voted down in a single day, that seems suspicious. But if there are a number of downvotes on single posts then that is probably sincerely not popular by more than one person. I see both kinds of activity on your questions (yes, the first kind looks weird). Since you have a lot of positive activity on most questions, I'd take the multiple downvotes on a single post as something is wrong with thatathat particular post and try to learn from it (like in the 'german vs germane' question title, which you did).
- there is a high cap on the daily rep points earnable. There could easily be a cap on the other side for number of points you can lose (but I don't know if this is the case). You can only lose points by getting downvoted, or downvoting others (and also by others changing their upvotes and accepts if you edit your posts but that in a sense just means you didn't get the points in the first place). Whether, there is a low cap, I think that the current down rep values and ability to vote limit the damage that can be done.
- despite that, what do you think a good low cap would be? -10, -40, minus something else?