What distance would you recommend for a 120W QB288...

I started my seedlings under a 600W LED, and as it was my first grow, I followed the instructions that came with the lamp: placed the lamp at 24 inches above. In retrospect, now that I've learned a bit, turns out it was too powerful and while it didn't cause any visible damage to the plant during seedling & veg phases, I believe it softly stressed her and prevented her from growing full sized leaves. When I compare to her clones now growing under a 300W LED running at less than 25% intensity, they are developing much stronger stems and much larger leaves than their mother, at a faster pace. I've also been experimenting with three brand new seedlings. Two grew under 50W LEDs at 24 inches above. One stayed in the grow tent under the 300W LED placed 36 inches above. The first two thrived, the one in the grow tent grew much more slowly. I ended up moving her under the 50W LEDs and within hours, her leaves pointed straight up. Hope this helps.