Hey mate, Pmal027 is right..
Don't change forw. and backw...
This will Stress your Señorita quite much.
Imagine you be livin comfortably under a 72 W CFL and all of a sudden the Sun is 15x stronger... what would you do.. Duck away, concentrate on surviving...
Your Damsel can absorb just a certain amount of photons,
I think you are just flooding her with light which she can't use.
I doubt that you really have true 1200W in your LED, but plants need to adapt light changes and that can take a few days. I would suggest to bring enough distance between light and plant. If she stretches - get closer
If she stays small Moore distance.
Good luck and happy trails for the rest of the way!
✌️
OimRausch