Why has my domain authority dropped significantly?

Why has my domain authority dropped significantly?

1. DA Checking tool - How are you checking your DA? If you are too dependent on one tool, have a look around and see how you rank with other tools. If you're using Moz, for example, try using a free trial and compare your rank with Alexa, Semrush or Ahrefs
2. Inspect your backlinks - Have you lost links recently? Have any new backlinks been recognised by your backlink tool? It could just be a matter of timing
3. Content – Have you removed content from your website , affecting the number of organic keywords?
4. Blackhat – If you have been buying backlinks, spamming forums, it may not be recognised at first but it will eventually catch up with you.