a) I can't believe that I've fluffed the Maths paper. This ok.
b) The rooster fluffed itself up when it senses danger. Your tenses don't agree with 'fluffed' and 'senses'.
c) Don't pay attention to his music fluff and focus on yours. I can't imagine what this means.
c. Don't pay attention to his music, it is only fluff, but focus on your own.
In this case I would imagine that a student of classical music might have told a teacher about some modern, light, and in the teacher's opinion unimportant music. The student is being reminded of the serious music on which he needs to concentrate.