When you changed your strings, did you have the setup redone. Most here will flame in for saying that, but I can tell you that Worth's are thin and I would guess they're not seating properly in a nut designed for more than likely thicker strings.
Personally, if I change a string set, I have in my mind that I'm also swapping out the nut and possibly the saddle. Why? The nut slots may no longer fit properly, and the saddle may have to be redone/recompensated. For me, the best time to change strings brands is when installing a pickup, and going to thicker strings - this way its just labor, and not material. Fortunately for me, Savarez and D'Addario are very very similarly gauged.
BTW, if I wasn't clear, setup costs are worth it, probably $50 USD or so, depends on the person working on it. Although, Kanilea sets theirs up pretty good to begin with. Of course, that doesn't matter in your case since you already changed your strings.
-Aaron