Too small? Too far from light?

Hi,it can be some reasons, not enough light, bad genetics, did you add nutrient to Coco coir? Coco coir is neutral soil, don't have any nutrients.

Your light is way to high. Drop it down so it is 10" from the top of the plant. Then slowly lower it to around 6". You will notice the light is to close when the leaves start pointing up. You want them to be flat or slightly dropping. Keep both veg and bloom on. You want as much light as you can get. If you do get a new light you want quantum board or bar style, that is not purple.

Im a newbie but from what i have learned and experienced over the last 3 months is probably your lights. Even though they compare it to the 600w its still only 100 true watts of electricity. With that i would try to drop your light 1-2" a day and watch to see how ur plant reacts. Dont drop ur light to far to quickly. I would try to get them about 18" away or simply if you can increase intensity of light

It's your lights not good enough what led do you use of cheap led then that's your problem

FYI this is the Royal Queen Hulkberry in my diary