Anyone with any sense of what has been happening with Google over the past few weeks and months will probably be aware that Google launched a MASSIVE update back in August, nicknamed the Medic update. Although it was mostly medical websites which were affected (hence the name), it actually affected a huge number of websites and caused rankings to fall for a massive range of different sites.
It now appears, around 5-6 months later, that businesses are FINALLY getting out of the pit that google caused with this update. Now we have started to figure out exactly what was being or not being penalised, we have had time to fix any issues to get sites ranking well again. It is thought that low E-A-T scores (expertise, authority and trustworthiness) were to blame for large ranking losses. The best way to claw out of this issue is to increase your quality of content. Make sure that your site is accurate, readable and a good authority on your topic and you should be fine.