Leaves curling down week 3 veg

[cr8grow]

Week 3 veg all four plants growing well. One plant has comical wide leaves that are starting to curl down. I up potted 1 week ago. All have been watered lightly and fed two days ago. Im not worried at this point since three are in great shape. My plan is for pots to get light and give the first full watering with nutes again at that point. Biocanna suggests I should increase Biovega going into week 4 from 1.7 tsp to 2.1 tsp per gallon. Everything is PHd to 6.5 before watering. Perhaps a little N toxicity on 1 plant? Stats from my grow journal #2 follow, then pics. In the group shots its the lower right girl.

The Cali Connection Corleone Kush feminized (Pre-98 Bubba Kush x SFV OG IBL)
Indica/Sativa (heavy Indica)
THC 18%
Flower 9-10 weeks (breeder 65 days)
Yield Medium
Indoor - Custom built cabinet (3’ x 3’ x6.5’ ft. H); 4” filter/exhaust, HEPA filtered passive intake, no light leaks
Plants 4
Soil seedlings - Potters Gold in Solo cups
Soil grow - Roots Organics 707 amended perlite, worm casings, silica
3 gallon plastic pots (full)
Light Sun System 315w CMH (1) - Phillips internal ballast; bulbs Phillips 4k (4200) veg, Phillips 3k (3100) flower
Light cycle 18/6 seedling, veg, 12/12 flower
Temp 65F dark / 81F light
RH 30-40%
Water adjusted to PH 6.5 - well (tap) average PH 7.5, PPM 142, EC 302 @70F
Nutrients - Veg Superthrive, Biocanna Bio Vega; Flower Biocanna Flores, Budswel guano

 

[Virgin Ground]

65° ambient temp. Root zone is too cold.

 

[cr8grow]

Current stats from yesterday Temp L 66 F (6 hours dark) H 84 (18 hours light)...would 66 for ~6 hours be too chilly? The other 3 are growing very fast and look great.

 

[Virgin Ground]

Yes. Some strains or even phenotypes within a strain can be less cold hardy.
If the soil is wet it is colder than the ambient temp by a few degrees. 64° stops uptake of mg.
The plants will also slow their transpiration and stop drinking. Pretty soon your plant is susceptible to root rot and various other problems.
Environment is very important if you want to get the best out of your plants.