Direct traffic can encompass a wide range of sources, including those you would have liked to have tracked in analytics. A drop in traffic from a particular source does not necessarily mean a drop in traffic. It could indicate a case in which that source ended up being categorized under Direct traffic. The best advice is - proactively use tracking parameters in cases where you may be risking not properly seeing traffic. There is actually a nice infographic showing the main factors impacting traffic. I use it sometimes to solve the current issues. Taking the right steps to address potentially miscategorized traffic, as well as being upfront with clients about the causes, can help to mitigate problems.
The term “organic traffic” is used for referring to the visitors that land on your website as a result of unpaid (“organic”) search results. Organic traffic is the opposite of paid traffic, which defines the visits generated by paid ads. Visitors who are considered organic find your website after using a search engine like Google or Bing, so they are not “referred” by any other website.