Even worse, there is no mention of reason as to why they down voted the post.
Of course, you don't have to give a reason for every down vote, since some posts are so low in quality and in no way we can make them better even after editing, so in such cases, we can down vote them without providing any reason. This is already discussed in meta.hinduism
The example I mentioned are by no way can be called as low quality posts (one of them is my own, where I added all the references from valid sources as per this site's rule while composing the post).
Of course, my worry is not the down vote itself(and loosing the reputation as a consequence of it), but this habit of fairly senior and expericed community members to down vote fairly well searched post without even pointing out reasons/comments.
As a community, how can we deal with this situation?