I don't know the answer to your question but the university of Ohio did an extensive study a few years back and they had a list as to what plants were affected and what were not. Maybe try googling something like "ohio black walnut study". Before jumping to conclusions try useing a systematic approach and be sure to think of not only what's going on in your yard but all the areas surrounding the tree. Any recent ground work or alteration to the yard in the last few years, such as any heavy equipment been on the yard, new patio, new pool, etc, etc. Has the anything changed about the run off into or out of your yard? Has the sunlight changed, such as another tree was cut down, or a building put up? Any other Crimson Maples in the neighborhood or area showing similiar signs? Any obvious signs of insect or pest such as bore holes, leaves being chewed? Try calling around the local nurseries and asking if any pest or diseases specific to that tree are around? That's all I can think of, good luck.