Answer: Based on your description I am not certain what is happening to the birch foliage. It is not so uncommon to see a black fungal infection or sooty mold on birch, but I am not finding a "typical" problem with red coloring. You might wish to consult with your county extension and/or local professionally trained and certified nurseryman or a professionally trained and certified arborist to try to obtain a more definite identification of the discoloration. Based on knowing specifically what it is, you will be able to determine what -- if anything -- needs to be done. I'm sorry I can't be more specific for you long distance.
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