Given that this is a mix of straight coco and peat, my guess is you need to pH for coco/hydro, which would put you in the high 5 range (5.7-5.9 I'm thinking, but I'm not a hydro guy).peat/coco mixes.
Is there anything in the description that stands out in your mind?
Do we need to prep peat like we prep coco?
Is there a pH range for peat like there is for coco?
Two other things come to mind...I hope that light is far off the plants if it's even half 1200 wall watts, because the plants are still small. Also, I think you can water in a smaller ring for now until you see more growth.