Ending of 1st experiment

One week have passed since I replanted spinach seedlings into hydroponic setup. Till this week not only seedlings didn't grow at all but they've also became weak and withered. Unfortunately I had to admit that my first experiment failed.

I allow three possible reasons which led to failure:
1. Most possible that amount of light from one bulb is not enough for plants. Yet it has high intensity of light output but its spectrum isn't as wide as HID bulb's.
2. Germination took place on mineral-wool for construction purposes. I am not sure but it could possibly contain some toxic elements.
3. I never checked Ph level of water. I think that it was about normal because seedlings germinated. But to be 100% sure I have to buy Ph-meter.
My next step will be a try to grow seedlings under sunlight near window. Very soon I will buy HID bulb. Then I will be able to try growing under fully artificial circumstances again.