I started growing these under T5 HO lights . just changed to led lights and the plant got super bushy and the leaves are curling up toward the light. light is about 12" off the top. am I to close?
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What LED are you using. If it’s low power that distance may be okay. If it’s a higher output, I’d have them around 36" to start and see what happens. You can always lower.
Also, did it come with a manual? It will usually show the correct distances for the particular light.
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For me LED’s always at least 18-20" above canopy. Any closer and have had issues.
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Leaves curling up is a heat stress issue
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I agree with @Majiktoker
With it being changed the ( light that is ) may give your plant an issue at first, re-check height of new light and give her a couple of days to re-ajust.
Will
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Are you sure it just isn’t the leaves turning towards the light after doing some LST? Looks like some string holding down the shoots. Those will turn back upwards.
Yes im sure there is a difference lol
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lol, I wasn’t questioning the heat thing at all btw. I was just making sure there wasn’t something we can’t really see behind the mass of green 
Oops my apologies misinterpreted
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But that really seems to be it other wise healthy plants
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No need man. You guys are the growing Gods and know your stuff 
And yes, my first thought was they looked pretty healthy.
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Answer:
This looks like the result of excessive heat. When the the serrated edges of marijuana leaves curl like that, it’s often a sign of heat stress from too high temperatures or hot spots.
When the problem is low humidity, the leaf will tend to fold in the middle, like a taco.
What’s your temperature in your grow area? Is there a hot spot around these plants from the grow light?
You mentioned that this is happening to only some of your plants. If this is happening to the plants which are closest to your grow light, that’s a hint that the problem may be temperature related.
If your light is simply too close, you can move the bulb further away from these plants and this issue may resolve itself. However, these leaves are showing symptoms of heat stress, without light stress (burning / spotting), so it’s more likely that the light is a good distance away and the heat just isn’t being controlled properly.
When growing with hot HID lights, good ventillation and an exhaust fan will go a long way. If the whole grow area is too hot, you will want to consider venting out all that extra heat.
Having good air movement, like a small fan in your grow tent blowing over the tops of your plants, can help prevent hot spots from forming directly under your grow lights.
In general, if it’s too hot for you to be comfortable, it’s too hot for your plants.
Will
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Gotcha. Great info and worth bookmarking for sure.
I just saw this and thought maybe it was making it appear more dramatic.
thanks for all the feedback. I should have done a little more research. ijust jumped in with the theory “closer the better” .pretty sure the led was just to close and burning the leaves. I moved the lights way about (about 30") and they are already responding
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