What kind of paper is in that planner anyway? Some of them use paper that's basically glorified tissue paper and bleeds if you look at it funny. Was it a fancy pen with wet ink, or is the paper just that bad?
Honestly, is it really that bad? I've had pages smudge before and still made out my writing well enough. A little ink bleed just makes things messy, it doesn't wreck your whole plan. You can always jot a quick reminder on a sticky note if one spot gets blurry.