Yeah it's been often referred to as "Facebook Zero" and in some quarters is part of FB's fight against clickbait and also to drive more and more people to drive traffic to their pages from FB Ads etc. What we're finding is that right after the time changeover (midnight PST or 8.00 am GMT etc) the level drops and then as activity on the page continues throughout the day such as more posts and likes etc then the Organic reach climbs.
What you will have to do is calibrate/monitor your activity to see what you can do to mitigate the drop on Organic reach as this can be done. We left a couple of pages alone for 14 days once just to see what the "floor level" was once and then we're now building back up again.
Bottom line is that you need to be constantly working a page and then when FB see more activity, more life and more genuine engagement the level of "Organic Reach Dropoff" will reduce..ultimately to zero and your reach will start to climb again.
At the end of the day all FB want are seemingly genuine pages with genuine engagement and basically adding to the overall community.
Provide that and you're good to go so not all doom and gloom
We launched a page yesterday with a couple of posts, no paid promotion and we used a little technique we've been working on and here we are 24 hours later with 132 likes, Reach of 412, Post engagement of 186 and 159 people talking about the page so it can be done...that was just a test to see if what we thought would work...would in fact work, so now we'll kick it harder ;-)