If you are experiencing falling Facebook numbers there may be a reason for this.
If you are promoting lotteries products, the Facebook algorithm will reduce who your page can reach. I have seen evidence of this. My advice to newsagents with lotteries is that they do not promote lotteries on Facebook.
If you have news in your name, Facebook may see your site as news related. Some are reporting a decline in traffic since the government initiated action seeking Facebook to pay for access to news. While I have not seen clear evidence of this, there is anecdotal commentary that it could be an issue.
Facebook is an evolving beast. Like anything you rely on in your business, it is not forever. It is important to spread your reliance across multiple platforms with on one thing playing a major role in generating traffic.
One option I have found success with is for the business to have more than one Facebook presence. This allows you to reach different people through different voices, from the one business.