What’s guys I’m new to this growing game. I have 4 auto plants. 2 seem to be doing pretty good and then I have 2 with curling leaves. And one is browning at the tips. Can anyone tell me what the problem is and how can I correct it? Thanks in advance!!
Here is a pic of Heat Stress
Answer: Heat stress.
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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Yeah the two that it’s happening to are the two that are close to the lights.
Thanks bro