You know, it's amazing how many people here are experts in nutrient lock-out and can determine that's the problem without adequate testing. Kind of like palm readers and those that read chicken bones, never cease to amaze. Your certainty is overwhelming. If a calmag product would halt the progression, I'd think that would prevent it from getting started in the first place. I don't know why everyone is on this calmag kick. Unless it seems to work because it can't be shown to be wrong, therefore it makes for good bullshit, er excuse me, good reasoning in this forum. If you really want to know what's wrong with a plant, the leaves should be sent to a lab. I'd be hesitant to trust anyone here who seems so certain yet what they say doesn't make much sense. Very little info was given but what I know is that those soils come with nutrients mixed in, just read the bag. Use enough of OF and it might last the entire grow.