No idea I am honestly a novice but I found I had problems switching straight over. I have read conflicting sides of what to do when you flip so a more experienced person might be able to answer that. I just know that the first 2 weeks of 12/12 you are stretching and to me that means grow nutrients and when flowers appear around day 10-12 that's when flower nutrients are needed. So maybe there is a deficiency there, meaning it might not be a cal mag problem but a whole nutrient problem? Can we see a picture of the whole plant? Is it all the leaves or just a couple? Have you tested your ppm/ph on your runoff, if you are soil, or tested your reservoirs ppm/ph? Have you changed anything in your normal schedule, added more nutes, fed more/less, feed nutrients every feeding etc? We are working with limited information to help you out. The more detailed you get the better.