I was also wondering is there any way that that rusting color could be from LED grow lighte being too close after watering.. my light is wicked close.. idk i guess i didng realize how long a foot really is .and dont have a ruler in house.. lol.. my 600w cob LED light was 2 dollar bills length away from plants.. moved it to 3..apparently a dollars 6 inches long.. was wondering if this could have done it .. although the taller healthier plant would then have been closer and showed no signs.. its wierd the most effected leaves were the middle growth.. not the lowest leaves or top new growth.. the middle ones.. soo thinking abt it.. they may have been closest to light.. bottom leaves too far.. new growth wasnt there long enough
I doubt it, LED's wont burn the plant, I sometimes have them touching the lights, it's fine. The best distance is at 2 feet with the 10w chips, I think 1 foot with the 3's and 5's and you can go as close as you want with the 2's and 1's, but if it's a powerful light, I would back them off some.
I just bought a 790 watt LED, it's what they call a 4000 series, anyhow, it's the biggest LED unit, I've used so far, and it's got a bigger footprint than the $2k Black Dog's, with more refined spectrum, so it's a fine unit to say the least.
I've got 2x of the 3000's and there drawing 470 watts.
The new unit's got 390 pcs (10w dual bulbs) are all running around 1.7 w each (so they last longer) 50,000+ hr life, The spectrum is as follows:
Full Spectrum:
280nm ~ 315nm -- Influence on morphological and physiological processes is minimal
315nm ~ 420nm -- Chlorophyll absorbs less impact photoperiod effect, prevent stem elongation
420nm ~ 500nm (blue) -- Chlorophyll and carotenoids absorbed the largest proportion, the greatest impact on photosynthesis
500nm ~ 620nm -- Dye absorption rate is not high
620nm ~ 750nm (red) -- Chlorophyll absorption rate "high", has a significant influence on photosynthesis and photoperiod effect
750nm ~ 1000nm -- Absorption rate, stimulate cell elongation, impact of flowering and seed germination
>1000nm -- Converted into calorie
It's a really well designed light, IMO, really pumps out the oils. Now this one might actually burn a plant...
But I've had the 3000's up along the edges (not in the center) touching the light without any problems. (although I was running them in veg mode, so only half of the leds where on).
Once both the red and the blue are running together, you definitely need to set them back some. My light meter maxes out if I get them too close, that's 100,000 LM I believe, at around 65,000 to 85,000 is the most plants can handle, after that, they start to do weird things. (ie. bleaching).
If you get a decent light meter, you'll notice the light changes from center to edge, significantly, So I put my tall plants around the edges, and my shorter ones in the middle.