What wattage LED are you using ? I have a 275W unit and at that distance it would toast the leaves fairly quick, I have mine at 18 inches with my flowering plants and it seems to work well, as your plants are ok it must be ok at that distance, light bleaching is fairly unmistakeable, it looks as you would expect bleaching to look like, if you get that on the leaves nearest the light move it up a bit.
A few weeks back one of my plants was about 8 inches taller than the rest which made keeping the light a correct distance away near impossible so I gently bent the top over by about 2 or 3 inches using some thick, soft wool and tied it off, the next day I pulled it over a few more inches until it was roughly the same height as the rest.
Its easy to tell by feel if you are pulling too hard and in danger of snapping something.
Interestingly after another week or so, the other plants had a growth spurt overtaking the one Id bent over, by now it had completely reshaped itself with all the side branches forming like the original central cola and was now about 8 inches shorter than the others.
D'oh !
I untied it and as expected it stayed in the position in which Id tied it. Double D'oh !
However after only a few more days it straightened up, realigning itself normally but with the advantage that all the side branches on one side are thick and full like the central cola.
Woohoo.
Sorry, waffling, good grass.
Should add one more thing, forgive me if I appear to be insulting your intelligence but you say you want to bend one of the main stems, you don't actually mean the stem do you ?
You need to attach your rope, wool etc to the very top of the plant where it is most flexible, the main stem will not bend without breaking if its a mature plant, if its still small, the same rule applies, bend from the top, again, sorry if Im stating the obvious.