You should also analyze the backlinks of your competitors. In case they have built good backlink profile recently, their website would rank better and rankings of other sites would come down.

There are many reasons, It's not simple to do recognize it. You can spend time for checking its

1. Manual or Algorithmic Penalty Rank Drop

1.1. How to Diagnose a Google Penalty?
This is usually a big drop in rankings, that happens over-night. If you notice that your site drops more than 10-20 positions on a multitude of keywords, this could indicate a penalty. A big difference between algorithmic and manual penalties is that the first ones are automatic and are usually released with various Google Updates, while the second ones are manually applied by a Google employee. Given the fact that Google made a habit out of making updates without clearly stating it, you should constantly monitor for ranking changes. You know you’ve been penalized by Google if the drop is harsh and swift, and you can see that your site continues to rank on other search engines like Bing or Yahoo.

Some of the main reason for rank drop get an link from low quality sites search engine not like this kind of link,buy the links also one of the factor for rank drop..

There are many reason for drop in ranking mainly black head technique like duplicate content,paid links,spammy links, and duplicate content etc.

1. New website Design/Redesign the website
2. Low quality links
3. Losing good links
4. Bad hosting
5. Competitors
6. Google updates

Losing placement on high-volume general terms can induce panic, even if the fall only continues for a few months frame. However, in the majority of circumstances, it is possible to find out exactly the reason why.

If it is new site, maybe because of dancing?

Spammy links
Duplicate content
Keyword Stuff
Over Optimization
Fast Link building
Low quality content