If it were my girls i would have given calmag every watering as coco binds/makes it unavailible for the plants. Im new to coco myself but i would have given an Ec of 1.0 to the girls at this stage(when photos was taken) with waterings every day. But it looks like your girls did fine with the the EC u had. Never try fix something, thats not broken. All i advised was to water your girls, not change of any EC, as all i saw was that the smaller one asked for more water around her roots.
Great idea with the timelapse! Then you can see how the girls react to different thing. Waterings, lights on/off.
I sure did grow some pretty big plants in coco, but im still very new with it. When i have learned how to really master it i will feel more secure helping out. I dont want to be the guy trying to know things, if im not sure - im not like that. But when i do know something, i love to help out.