I went down from 16% to 8% now.
I know the reason why my curation APR has gone down. I am now going for more engagement and expressing myself instead of getting more curation rewards.
Hive curation simply punish manual curators.
https://peakd.com/hive-167922/@r1s2g3/is-hive-curation-is-broke
I think some of your decrease may be due to other people tweaking their votes, mine dropped 2-3% recently and I've changed very little!
I guess there is the possibility that as the larger accounts grow more rapidly, the curation returns of middling accounts get reduced also.