Where were the ranks that you lost? E.g. was it top 1-3 in SERP that moved to 4-10 or was it 4-10 that moved to 11-20 ?
There could be many reasons, if you've moved from #2 to #4 on a keyword, there's not much you can do.
If you've moved from #7 to #21 for example, it's very likely that your...