I think overall the plants are looking pretty damn good. I just finished up my second coco grow, so I'm still learning. My experience has been that coco isn't as set it and forget it as lots of folks parrot. I also think it is possible to over water with coco, especially with smaller/younger plants. My experience, limited as it is, is that's a balance between plant size, plant health, container size, coco-perlite ratio, transpiration rate (related to environment), and fertigation frequency and volume. It's a real juggling act based on your particular situation.
A couple of observations based on my experience, which means none of this shit is absolute - I think I'm seeing some green alge on the perlite in some of the pots. If so, you may want to up the air circulation a bit, and it may indicated the coco is staying too wet. Also I think your input ppm is a bit high for those size plants. Keep an eye on run off pH and leaf tips. I have found, with high frequency fertigation you don't need to feed as high of an EC. Just as a point of comparison, in my last round at peak flower, I was feeding 5x a day with 650 ppm (EC 1.3). Granted, to a degree that may be strain related. As I said just as a point of comparison.
Good luck with your grow!