The curling started at the top like it is currently at the highest pair, it becomes like this after 2 days
Details: 76F, 65%, RH 1.08 Vpd, viparspectra xs1500pro at 16in 50%, fed with fox farm trio+kangaroots and calmag, they’re fed with half dosage and whatever the schedule calls for one week behind how old they are (40 days), planted in fox farm light warrior in 3 gal pots
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How often are you watering or feeding these plants and what’s the run off PH/PPMs 
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I Water when medium is completely dry and kinda clumps together, feed between waterings. I haven’t looked at runoff yet but I will next watering and lyk
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You should water when the potting mix is partly dry, not completely dry. Stick your finger in the top 2 inches of soil and if it’s dry, then water it.
The plant on right has a nutrient deficiency on older leaves and needs more fertilizer (or fertilizer more often).
The plant on left has burnt leaves that could be lack of water. Plants from the same batch can and do use different amounts of water. I had a number of plants from the same set of seeds and one used heaps of water while another used hardly any and the others were in between.
Cannabis plants can take a lot of light as long as they don’t dry out. They can also use a lot of nutrients so regular feeding is recommended.