Answer: It sounds as though algae or lichen is growing on your red maple. This can happen when trees are planted in shady areas where moisture is high and air circulation is poor. You didn't say how long the tree has been planted in its present location. Perhaps neighboring growth has gotten so large that it is inhibiting healthy growth of your tree. I would prune out the bare branches in hopes of encouraging healthy new growth. The algae or lichen won't damage your tree but it does look unattractive. This winter you can spray the tree with bordeaux (lime sulfur) which will kill the lichen/algae. It will eventually slough off with rain.
Make sure your maple gets a deep soaking once each week. Good soil drainage and adequate water should take care of the droopy leaves.
Best wishes with your maple!
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