Too much light?

Seedlings in coco can be tricky, and I love coco! I was initially going to say no, as your seedlings looked to be stretching quite a bit. From their structure I would have said the light was a little too low. Then I saw that your 240watt qb was 8 inches away and that gave me a little fright! But I noticed you have it dimmed down, so I don't think the light is entirely responsible (although being too close/strong could exacerbate nutrient issues). You can look at my Euforia journal for a coco grow plant that I over lit a bit. I grow very similarly to you in coco, frequent fertigations, GH flora, etc , so I like what you have going on! But an EC of 1.1 this early is really high. I think this is the cause. I would have it at half, with about .3 going to cal-mag and .3 going to base nutrients. Then slowly dial it up to .8 maybe if the issues seem to reverse and the plant grows another node or so. I wouldn't go to 1.1 until mid-late veg at the earliest when the roots have been well established and the plant is happy with it's environmental conditions. Hope this helps, feel free to message me if you have more questions. Happy growing! 🌱👍