The Hi Yield Calcium Nitrate is for use on tomatoes to help stop blossom end rot from occurring. We are unsure if it would do anything for apples or the bitter pit you are referring to. Our team does not have experience in bitter pit or what would cause or eliminate it, so we would recommend reaching out to a local fruit tree nursery or your counties master gardeners office for assistance with this particular problem.
Hi-Yield Calcium Nitrate does not have instructions on the product label for application in hydroponic systems so we are unable to recommend this use with the product.
