if the only way to keep circulation going & heat down is your extraction fan-- then 24/7. if you have a passive circulation system or you're in an open area or are able to open the tent-- you can probably get away with using an oscillating fan to keep everything moving when lights out
If your pots drain/ dry quickly it can lead to being underfed/under watered...
I don't worry too much about ppm doing the soil thing or pH... could be simple N def.
I use GH too, but I amend w/ organics also...
how long you planning on vegging them? what height you plan on finishing @? when you put em' to 12/12(flowering) it'll take a couple of weeks to pre flower, then figure a couple months to finish-- n it should be 2x as potent than your auto was... or if it comes out not-so-good, comparable to...
re: Is this heat stress?
throw in some epson salt (Mg) + bloodmeal(N)-- top dress/water it in, your plant almost looks "see-thru" & pale looking... get em' a deeper green...
you'll get faster results if you foliar feed-- hit em' in the roots w/ a good drench too...Aloha!
Good job!! taking it to the finish!
...couldn't help but notice the stalk & stem color-- looks woody/dry... I would guess underfeeding/root issues.
when you reclaim the soil check the rootball to see how she grew out... whats in the pot after you chop will give you a good read on how you did...
strange can be good, for sure! maybe she hit a hot spot in the pot or something when rooting... causing her to mutie a bit? i'd keep an eye on it since you're keeping her... don't want any hermies.
Aloha!
you should be running FULL strength transition nutes-- plants look big enough to handle it... JMO in what I've noticed, sativa dominant strains beg for more Mg, N, P (epson salt, blood meal, bone meal, + for a kicker add some molasses).
I'll top dress & drench it in w/ the molasses... this is in...