I have always used LED lights at 100% from day one to finish and both the veg and bloom lights switched on together from day one until harvest too.
I believe plants in veg grow better with both lights turned on and getting all the spectrums the light can provide. Just don't get too close early on and it should be fine, cannabis is "designed" to grow in full sun, so a LED is not going to harm it if it is far away enough (24-30 inches) and as long as ever there is good air circulation.
I would suggest a 6 litre pot is not big enough, something in the 10-15 litre range would be better, and you could still use your current irrigation system, but 6 litres is not going to allow for much root growth, even if it is an air pruning pot (which are GREAT BTW), just the plant can only grow as big as the root system can support it and if you want to grow the "one and good" plant, 6 litres is putting you behind the eight ball from the beginning.
Hope this helps,.........
Organoman.