As I recall, CASE stands for: Copy And Share Everything. I've also seen people phrase it as Copy And Steal Everything, but that seems a bit harsh.
To go back to the original posters question if you are changing paper, and the sentiment or making other small changes I think you're okay.
This topic comes up a lot and the comments that make the most sense to me are the ones that mention, how can we be SURE we've come up with that layout, that color combo, that "whatever" FIRST??? With the multitude of blogs, magazines, YouTube videos, and lets not forget Pinterest....how do you nail down the VERY FIRST use of your layout or whatever?
As the Bible says, "there is nothing new under the sun". Fashion designers are almost always "reviving" some previous decade or trend, small changes are made...and "voila"! It's all NEW. And they make money on it hand over fist.
Also, as others have said, it's paper and ink. If someone used a design they were taught at your class and won a competition with it; good for them for taking the initiative. However; I do feel it's important not to take another artists stamp or digital designs and using them as if they were your own and making a consistent profit on someone else's work. Independent artists deserve to earn an income too.
Mary in NC