Tips pointing down and starting to twist?

What is a good place to start when the leaf tips are "cupping" down. One has the leaf edges curling up, and another plant has some yellow stripping going on. I came across these photos and info and wondered what could be causing these problems.





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Info:

600W HPS
Lights 20 inches away
Temp at base is around 65
Temp at tops are around 75
Light fertilizing
PH of soil is 6.8 to 7.0
After fertilizing soil PH drops to 6.5 to 6.8
Fan blowing lightly on plants
Watering every 3 to 4 days, with 16 oz.
At tops of plants, light metered used stating a range of 4000 to 5000+ lumens

Any advice?

The stripes look like a micronutrient def to me. Zinc or sulphur maybe? The curling up is usually due
to inadequate moisture or heat stress. Sounds like your temps are good though.

What size pots are you using? like muertos said every thing sounds good i think you maybe under watering 16 oz is small thats only 2 cups.

wats ur humidity at?cud be the prob!

Pot size is 3 gallons, humidity....not too sure, readings are different from different meters, one states 25-30%, the digital sometimes just says Low, then others after watering it says as high as 75%, so I don't think it is very accurate.

gbran210 said:

What size pots are you using? like muertos said every thing sounds good i think you maybe under watering 16 oz is small thats only 2 cups.

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I wondered if 16oz was too much or not enough. Before waterings, the probe moisture meter states the soil is dry when stuck half way down into the pots. After watering it says the soil is "Wet", then it usually takes 3 to 4 days to get back down to "Dry" reading.

noxiously said:

I wondered if 16oz was too much or not enough. Before waterings, the probe moisture meter states the soil is dry when stuck half way down into the pots. After watering it says the soil is "Wet", then it usually takes 3 to 4 days to get back down to "Dry" reading.

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i have 4 gal pots and water 32 t0 64oz..i wud try 32oz of water

pics didnt show for me, but usualy a twist is ph, tips curlinbg down is lack of food. you ph is to high. lower to 6.3 for feedings and waters if this is in soil or soiless