Excuse me here I can't reveal the website url here due to the confidentiality.
Background:
This website has about 100+pages, and is a wordpress site. Out of 15 targeted keywords, there are few ranked first on Google.co.uk. others are ranked between 3rd and 50+. In the past couple of weeks, we have been submitting to various websites/directories. and 4 main keywords' rankings are improving steadily from 50+ to 20+. We don't buy links, or pay for link exhcanges. We only exchange links on rare occasions.
Symptoms:
1. 2 out of 4 main keywords dropped its rankings from 20+ to 80+ 4 weeks ago over night.
2. We kept on acquiring links from directories and websites, and 2 weeks after the drop, the rankings of 2 affected keywords had gradually made its way back to 20-30. Just we thought the glitch was over, these 2 keywords has dropped rankings to 50+ once again.
3. The change of rankings looks too suspicious to us, so we went to use the Moz tool, and discovered the domain authority has also dropped 25% of its value in a month time.
We never experienced such violent changes in terms of rankings in such a short period of time. My question is: what factors there are to have caused such violent shifts? Why the value of the domain authority is dropped by 25%-30%? What elements affect the domain authority the most?