Going from 12 mg/mL to 8 mg/mL is a pretty big reduction (33%). You'll have much better luck tapering down slowly. I'd try 11 mg/mL for a week, 10 mg/mL the next week, and so forth. Then in a month you'll be down to 8 mg/mL and you will probably not even notice the change since it will be so gradual.
Yeah I noticed that yesterday just chain vaped the hell out of the 8mg without satisfaction, the 12 is ok I don't chain vape it constantly but it does give me a slight headache and raises my blood pressure. I'm going back up to my local vape shop tomorrow and see if they can make me a batch of 10mg juice and see how that works.