1st thought is burn from the initial look, either light or wind. I do not know LED lights to say if they are too close or not.
Do you have one of those USB microscopes to take a closer look at exactly what is going on?
I had similar recently, looked like P or calcium deficiency, turned out to be black mould which was visible under the scope but just looked like necrosis to the eye. After I cropped I found the dripping leak which had sent my humidity through the roof.
Does look a little odd, not a deficiency AFAIK. The damage is only on the top of the ridges and the edge, could it have rubbed against anything?
835 seems high for nute strength to me especially in RO, I don't go over 700 even in full flower.
If the only change was increased nutes and as it is only top fan leaves, maybe either reduce nutes or raise lights to see if that helps?
It might be that the lights were right on the limit and the extra nutes just pushed some leaves over the edge and they closed pores and overheated.
Or as Jellypowered said, PH. I find there is a dead spot between 5.9 and 6.5 or so, you either want to be over 6.5 or under 5.9, not between. Sometimes new clones like a PH of 6.5+ whilst established plants very much prefer under 5.9
If it is PH, keeping your PH under 5.9 should show results, if not I would cut back on the nutes a little.