If the ends of your leaves have a burned appearance, it's a fertilizer issue.
LED's give off so little heat that they cannot burn plant tissue. Even if the plants are growing very quickly, as they're wont to do at 1kµmol, if your fertilizer is properly mixed, the increased transpiration due to growth will not cause nute burn.
If you're getting tip burn, check your temperature + RH and/or adjust your nutrient strength.
I grow my plants, routinely, at >1kµmol and the only time I've had nutrient issues is when my VPD was cattywampus.
Light values for current grow are below.
Averages are near 1kµmol with some spots as low as 800, others at 1100+. The plant on the left had an area on one leaf that developed nute burn, maybe 1 square inch. The smaller plant on the right had a few leaves with a nute issue - check the leaves at the front of the plant in the lower photo. That popped up about 1 week ago and it's gone now.
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