Your first misstep; " I flushed with normal Ph 6 water, no nutes" You're not helping your girls by doing this. If you're running coco, you should always have some sort of feed % in your water, even if you insist on doing a 'flush'. Plain water is a no no in coco.
I have found the best success with coco, by matching my plants to my pots. In this case, coco plants don't need to be in giant pots. The coco is more a connector for your feed to the plant and it supports the roots...the coco by itself is not feeding your plants, like soil would; you're the one feeding the plants, so huge pots of coco are not necessary and make the balance between feeding and plant a bit more challenging.
What is your feed pH going in? Aside from your 'flush' have you been using plain water at all? Do you know how much Ca and Mg is in your feed, before adding the CalMag? These are all things I would look at carefully.
In my opinion, your flush didn't help and if you've been using plain water along the way, it's not helping. Secondly you're going to have to balance your moisture levels with your plants and feed schedule. Thirdly, your plants appear short on Mg, so instead of adding more CalMag, I would simply foliar spray them with some Epsom salt. If they green up, and they most likely will, you'll know what direction to head in. Good luck.