The ones that are purple off rip normally end up with more of a black look in the end.
It might not be a Cal Mag issue you're having. It looks to me like you might just be blasting it with more light and nutrients overall than it can handle. That solution temp it's pretty gnarly too. I'll be updating my dark devil tomorrow, check it out if you think it might help. Mind you it's actually a week younger than what it says. ✌️Peace homie and good luck to you.