In my opinion switching playstyle isn't really a good idea mainly because it takes a lot of time to re-learn everything, so just stick ddkk since you are already able to play 6*.
Also im not sure what you mean by "accumulated" notes, my guess is that you are talking about long streams. If that is what you are talking about, then there are two things you need to focus on: reading and stamina. if reading the note colors is fine for you then the problem is most likely stamina related. I myself am a kddk player but it took me at least a year before I could play long streams of notes consistently while there are others who took less time or have spent more time than me and still can't play long streams. Everyone is different and for you it might just be taking a long time.
I personally think you should practicing 6* for maybe 30mins each time you play instead of all the time, usually practicing for too long might make things worse.
hope this helps
