I've seen some cuttings take some time to establish. First they root and then they start growing slowly to establish before they start growing well. In that same time a seedlings can often match it's size. I've seen plants reach 18 inches tall and 4 inches wide from seed in 18 months. I've seen 12 inch cuttings reach 18 inches tall and 4 inches wide in 18 months from the day it was cut.
The lights are just 5000K LED, about 26000 lumens... 6 to 8 inches from seeds, a bit more than 60W per square foot. Some seedlings turn purple, it's a sign of health actually but not all plants do it, it has to do with genetics. The idea that the purple is a bad sign couldn't be more wrong.
Genetics play a role in growth rates, heterosis is a huge factor. Hybrids like PC grow much faster than pure species and PC grows fast but not that fast. Pure species display inbreeding depression and a hybrid from seed doesn't take long under ideal conditions to rocket past them in growth.
A lot of what people report, for example about seeds verses cuttings, comes from poor conditions as well as misconceptions about care and ideal conditions. I've got 8 month old seedlings growing inside a baggie for example, they aren't even an inch tall and wide. Just because a method works doesn't mean it is good and a lot of the experts do not actually know what they are doing. It's funny actually, because my results aren't even that good, if I transplanted earlier and didn't have issues with gnats the plants would be much larger. What I depict is good compared to some but it's only so so in my experience.