Bill,
Glad the alkalinity is improving for you. I still think there may be another problem. Organics, nitrate,phosphates, toxic metal,salinity? I'm sorry to say your corals may not recover; once a downward spiral starts it often continues even when conditions are improved. . If they were mine, I would frag a few pieces and try to regrow the colonies. Cut a qaurter to a half inch into healthy tissue for frags to get ahead of the dying process. Good Luck.