@sourdieselyumyum
Thanks for that info friend.
If you wouldn't mind, I'd like to explain my own experience that I have had with LED, earlier this year, I had an electrical issue at my home, and had to get an electrician over to do a few hours of work, which forced me to have to move my plants from the closet setup I had running at the time because that closet was right where the electric box in the house was located (electrician needed in there), and I had to use a generator for a bit, to keep the "fridge" cold.......n the lights running....
So anyhow, I setup some extra LED lighting in a separate room along with a few cfls to keep the (vegging) plants happy while the electrical system was being worked on, the room was much larger and I didn't have enough light coverage at the time, so I ran some LED strip lights that I had l been given by a good friend to test & see if I could get any use out of them, these lights were 6500k integrated type strip lights that people use in garages and so forth, so I had hung these lights up about 3 1/2 feet above thinking it wouldn't be much of an issue (this was my first year with indoor LED, being outdoor/greenhouse grower beforehand) and because it wouldn't be for the whole day I didn't worry initially, however this experience changed the way I look at LED afterwards, because within 2 hours I had young seedlings falling over on their sides like cotyledons to the dirt with the stem arching over, these were Basil seedlings that I had next to my plants that first gave me a warning as to how far my LED light was running above my plants, and these showed the first signs of shock that caused me to raise the lights a bit higher, rearrange the plants a bit more, and place the shocked seedlings in a separate room by a windowsill for that remaining tine afterwards.
None of my Cannabis plants were greatly affected by the LED lighting luckily, but the largest plant closest to the LED did have some signs of damage on the leaves, signs of photon/light toxicity/burn and so forth.
Now I know I sound a bit inexperienced with the telling of this story, but I can't say that this did not trigger me to further my understanding of LED technology, because it did, and I immersed myself with the understanding of it, and my understanding of light spectrum frequencies as a whole, and now able to teach others what I've learned and share.
One thing I will say is that the value of having an adjustable dimmer switch is almost priceless when it comes to tighter quarters & confined spaces, especially for when new plants are just getting acquainted to their new light source and so on (Sorry I know hindsight is 20/20, I've been in those same shoes you're wearing, sucks).
With the 600h r spec, you've got some serious photon output coming out of that machine, and at 3500k you are kind of mid range on the overall light intensity wavelength scale of things, which indicates that the light fixture could be used in closer proximity to the tops of the plants, however some varieties of Cannabis can be more delicate in regards to light intensity than others, this could be part of what had occurred to the plants that you are currently growing, and even at 4ft height seems to have overwhelmed the plants a bit initially, and with the spread & coverage that the 600h puts out, it does seem without ability to dim them down on intensity, that it may be necessary in the future to raise the light as high as 6ft above for the first few days, we are talking about one of the largest single light fixtures being offered in current production, it is a serious machine, there is no doubt about it.
I've had people doubt why I advocate to proper distancing between plants and their light fixtures, up past 4-5ft even, this is why, and the example I provided above is why, and in saying this, real world testing is advisable to know for certain which lights can be used and at what distance, and the corresponding amount of time it takes for plants to adjust to any new spectrum and so forth. Not all LEDs are the same, so this rule doesn't apply to every single diode type out there, but this thought should be kept in mind when putting a new setup together, and or around new plants or seedlings that may need further assistance and care for optimal growing conditions to be manifested.
The last thing I would like to mention as a piece of advice is to add some UV lighting to this setup if you are able, the plants would be better able to harvest more light if UV was added, UV triggers the plant to synthesize light harvesting proteins, carotinoids, and other cellular molecules that assist the plant in its light harvesting endeavors, added UV also boosts overall terpene content and flavoniods such as quercetin for example.
Here's an article that you may find interesting.
Despite controlling a diverse array of regulatory processes in plants, UV-B wavelengths (280–315 nm) are attenuated by common greenhouse materials such as glass and polycarbonate and are therefore depleted in many commercial growing environments. In this study, we analysed the architecture...
www.nature.com
Anyway friend, I'm sorry to see what has occurred to your plants, I hope this message can help us relate to each other in this issue together and that we can help avoid any further issues like this in the future, take care now and thank you for your time.
They burn all my plants to hell. I've lost 3 valuable seedlings and one of my mid flowering plant burned like hotdogs on a grill but hopefully she will finish in 3.5 weeks. I now have 4 seedlings struggling for dear life as I've removed my stand-alone QB and replaced it with a couple of CFLs.
