I am going to sit in the corner and watch, How often are you watering these? All they need is damp soil, let the top dry up about 1", mist them daily with a sprayer, and when you water, water the outside of the pot, not the stem, this encourages the roots to seek moisture. A large root system is the key so give them plenty room. I have 2 in coco coir right now that are 10 days old today since they broke and they look like your BL4, but they are under a 18/6 LED so not really comparable.
Its been 35+ years since I did my last outdoor grow, but I always started them indoors in the spring, (mid-March) temps were 70+ degrees with all the sunshine they could get from the window, around May 1st when the ground temp was around 50 degrees and they were 6-10" tall they went outside in the ground with a waterwall around them in case of a late freeze (these also provided a greenhouse effect during the day sunshine)
I was up by the Canada border so conditions were quite different than California, but 6-8' trees in a 5-6 month cycle were the norm for me with 2-3 lb quality yields per plant.
Rushing this plant will only cause you headaches, don't over water, over feed, or try to rush the growth, all it needs is moisture, sunlight a little food and lots of love and it will pay you back!
Good luck!
OTM