What watt is your panel? I was keeping my 180w like 20 inches and the plant was growing slow as fuck I lowered it too like 6 inches away and its lookin better than ever
Read your plants. Start with the recommended height and adjust from there. I end up adjusting mine at least once a week until the stretch is done. If your plants leaves are arched up soaking in as much light as possible, its in the sweet spot.
Depending on the led board you will want to be 1-8" above to avoid light burn. You want to be about 2 further back than burning, so really you are looking at heights of 3-10" above once the plants have established roots, much further/less until plant has established decent roots (first week).