For me personally, for my juices I find the best flavor on most Smok tanks comes in better around the bottom end of the recommended "best wattage" range. I don't know how many flavors you have and like, but I will rotate around 6-8 every day. I believe most juices just seem to work well in one tank and not so great in another. So I have multiple tanks using different ohm coils for certain juices, some I hit on a Atlantis or sub tank around 30 watts and others in a Big Baby tank around 58 watts. I tried one of my flavors I really like and use in a Big Baby tank, put it in the Prince and it just wasn't there. But another flavor seemed even better in the Prince. No idea if something similar is happening to you, but try some other flavors in the Prince and see how it goes.
What wattages did you try with the X6 coil? And how long did you try your juice in the Prince? I'm still fairly new with the Prince, so it may just take a little time for the coil to come into its own so to speak.