Answer: I doubt that the rocks are causing the problem. If you sprinkled a fertilizer that's meant to be diluted in water first, it could have damaged the roots. Concentrated fertilizers can "burn" roots--that's why it's always important to dilute them accroding to label directions. If the tree has been there a while, and has done fine in previous years, then I would suspect an insect or disease problem. Inspect the leaves, bark, and twigs for any signs of insect or disease problems.
If this is a newly-planted tree, you may have poorly drained soil, and your tree is literally drowning. (Roots need air as well as water...) You might need to move the plant. (If it's been doing fine for several years in that spot, however, then that's probably not the problem.
Maples don't like to have their roots compacted, so if you've done any construction work nearby, that could have been a factor.
Sorry I can't be more specific than that. You might check with a local nursery -- bring a sample in a sealed plastic bag for them to inspect.
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