It has been my experience with store bought juice that it may taste great at first, but after
vaping it for a while, it isn't as great as originally thought. Conversely, first tastes are so-so, but then grows on me after a while and becomes a good flavor. I try to take that into consideration with my DIY juices as I get into it more and more. This being your first mix, it is understandable it would be really good at first but after that newness wears off, might seem to diminish. That is one of the reasons I change flavors frequently each day to "keep things fresh." You might put it away and go to something else for a few days, then give it another try.
As others have mentioned, there may be other possibilities that adjustments to your mix may help/fix. Be sure it is "broke" before searching for a fix. Then again, if you have time, playing around may result in an even better brew!