When I first got my Digiflavor Siren and started using it, the first thing I noticed was that I (like so many others commented on) was going thru a lot more juice that normal, so I did a test. Before the Siren I was using my Lemo V1 (for about 2 years daily) and had already charted my usage, per day, and found that I averaged 3.86ml's per day of 8mg/ml juice. When I started using my Siren my daily consumption went up to 6.12ml's per day and it seemed that I was taking hits every few minutes all day long, so, as a test I upped my Nic level to 9mg/ml and tried that for 3 days, and found that my daily consumption went back down to 3.9ml's average, and have kept it there ever since. I never got Nic'd out or anything with upping from 8 to 9mg/ml's, and didn't notice a difference in flavor, just that with the Siren I had to up my Nic level just to use the same amount daily. So, even a 1mg/ml change will be noticed by you're body, one way or the other. I still use my Siren and still am at 9mg/ml Nic level. I too suggest that when you change Nic levels, just do it by 1mg/ml steps, and watch for any changes in you're vaping habits.
PS: What you did was to drop your Nic level by One Third, that's alot.
Edit: My wife says that I'm .... about things, I don't know, maybe.