I don't know exactly what you mean. I started off my seeds with the LED's only a couple of inches above the top of the soil. As the plants grew, I raised my LED's on their chain. Also, I have more than one shelf for seed starting and growing, so I was able to keep one shelf for seed starting and using the other shelves with the LED's higher for the growing plants.
I did not have any of my LED's 14 inches above the plants, nor turned down 50%. I supposed it depends on what the light output of the LED is? And I just bought shop LED lights on sale for half price, about $10 per 4-foot light, and not the "grow LED lights" that they sold for ~$60 or more per light. I did read the specs on the shop LED's I bought and the lumen output and the color balance were withing the plant growing spectrum. Good enough for me, and evidently, the plants as well.
Not sure what you think went wrong with your starts. However, my tomato plants got to be almost 12 inches tall before I transferred them to the raised bed gardens. They were a lot taller than I had expected. But their root system was in great shape because the net cups air pruned the roots and none of the plants got root bound like some of mine did back when I used solid walled pots.
I have become a big fan of using net cups for seed starts because I had great success with them. I plan on doubling my starts next year. I am even considering buying additional sizes of net pots.
I am also of advocate for bottom watering and letting the potting soil soak up the water it needs. This is the first year I did not drown out my seed starts. I think that all the open air around the net cup walls allows the plants to breath even if overwatered for a short period of time. In the past, I have drowned out lots of plants. Maybe it's a combination of experience with past failures and the net cups this year that made everything successful.