May not be significant, but I noticed that the fan leaves stems are purple on top and green on the bottom. Light too close?
3x3, 240 watt light. 16 inches from canopy.
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240 watt at 16 inches should not create any issues. You got a pic you can post? I would personally not worry about what you are describing. Welcome to OG @Fng.
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@Fng As Doug said you probably have nothing to worry over !
If the plant looks healthy and the steams r purple I consider it a “suntan” the plants way of coping with bright light …
This is a good thing .
Now just watch for irregular curling or tacoing of the leafs …
Then the lights maybe a problem !
Best of luck stick around check the place out !
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It can be a sign of Phosphorous deficiency, check the other signs to see if it’s your case:
but also can be strain related, as I hope is my case … 
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Looks like rhubarb! What strain is that?
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Herijuana x Mango moonshine kindly gifted by Pedro_Bann, too close to leds so maybe Rabeats2093 is right … 
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Welcome to OG @Fng!
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It can be a sign of overwatering i found out.
I generally assume that it’s basically a “sunburn” when it’s only on top like that. Often lower or shaded leaves don’t have the “sunburn” at all. I have a plant in flower right now that has purple on the top side of petioles toward the top of the plant, but petioles on lower leaves are either fully or partly green still. That said, I’ve seen other people argue until they’re as purple as the petiole that there’s a P deficiency at play.
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Yes phosphorous def usually caused by lower uptake , but only thru process if elimination will you know why uptake is lower : ) as long as the stem etc purpling dosnt progress and don’t thin and become brittle and woody you’ll be fine
Lack of uptake from low temps especially with lack of radiant heat from led , overwaatering , lack of enough p in feed etc only man on the ground can work out why : uptake or p is low )
The purple faced people are only trying to help lol
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Completely normal and inherent to many cultivars, enjoy the show!
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Maybe, or maybe they just have problems conceding when they’re incorrect.
But when someone posts pictures where a petiole has been partially covered/shaded and is green under that part but purple where exposed to intense light, it’s hard to agree it’s a P deficiency. In that scenario it’s more likely the plant is producing extra anthocyanin for photo protection of the petioles. Especially when the stems remain green as ever.
Cold air falling on plant from above ( only exposed parts to cold is purpling )could cause that maybe as I say the man in the ground is best to work out
We never know the full story just what they say or show which is limited so we alllllllll just guessing ie more likely : )
plant wanting to use intense light but uptake not able to match because of lack of radiant heat
Why not low p from too intense light for the lower uptake creating an effect similar looking like sunburn : )
I’m trying to help and work with you , I have no problem conceding if what you say is a fact : )
Temp / uptake not in balance with led light intensity
If I seen praying of upper fans then that may /would indicated to close to lights and how I would expect plants to react if light intensity was the sole culprit
Just shooting the breeze
: )