It is a little difficult to tell from your description. If the gap is between the backsplash and the wall then it could be a few different things. First off, the reason I'm a little confused is that I don't even really know how you would scribe one of those curving backsplashes, other than to beltsand the side that faces the wall wherever there was a high spot.
possible causes:? - The particle board absorbed water and/or moisture, swelled and created a slightly larger gap. - The studs and wall shrunk and pulled away slightly (if the framing was new). - the floor shrunk, or bowed down, bringing the front of the cabinets down and thus pulling the top-back away from the walls.
I like the first scenario. A 1/32" gap is not very big. If you want to eliminate it I always use Phenoseal calking. I would use the translucent or a close color to your wall or backsplash if they are similar colors. You apply this stuff and then you can tool it with a fine damp sponge to make a beautiful seam seal. It is long lasting, easy to tool and the translucent sort of takes on the color of what is behind it so you really won't even see it. I don't use anything else in kitchens. Silicone can be a nightmare.