As for the first set of pics, if those girls are already due to be transplanted, then I'd go ahead and transplant them...not like there's anything to lose if it doesn't solve the problem. So, was your PH in line when the symptoms began appearing? I'm not very experienced with soil and soilless mediums, but I do know that looks a lot like a magnesium defiency in a lot of ways. You may try foliar feeding some epsom salts to provide some immediate relief in the short term while we figure out a solution. So, if it were me, I'd foliar feed some epsom salts, and then transplant. The issue could very well be that your plants have simply eaten up the available magnesium. If a full strength epsom salt foliar feed doesn't make those symptoms stop spreading to new leaves, then I think it is safe to say that magnesium isn't your issue. Or at least isn't the core cause of the issue. If your PH is in line, then there may simply not be enough of magnesium and/or calcium it in your medium. Particularly if flushing the medium only made it worse, as you would've been flushing what little Mg that was present out. Good luck buddy, hopefully someone more experienced with soil growing can chime in here. I do not believe that your problem is lockout though, as you've really not added any nutrients to the medium. Lockout typically occurs when people go adding nutrients to a medium that already has adequate nutrients. Those leaves are so dark green, I would opt for epsom salts than calmag as I'm only seeing Mg symptoms there, and Calmag products contain N, which it seems your plant has plenty enough of.
