hey man, that a nice looking lil GIRLIE?!? looks like a budder, but! lol man be caeful, because if you stress it out too much, depending on the strain, it could go hermie...
that sure as shit looks like heat sress, but man, not much heat... hmm
a bowl of water near the plant will add enough humidty, every 10degrees F above 75 the air is capable of holding i believe 20% more humidity.
or, the more heat the more humidity you should try and add. but those temps, just dont seem that high, but, your plant is showing the stress.
looking again, there a few tips visible that are winding, or turning, that too is another sign of heat stress. WTF?!? my maui bigbud's top didnt show signs of heat stress untill it actually touched the bare metal halide bulb and burned some leafs haha, ugh.
different strains though, they want different things. you dont know what you have there? we might be able to tell here soon by all these lil quirks, remember, the first time, is just learning, which it seems youve done a goood amount of so far! your plant looks very nice, very managable, and structured. a nice pheno.
with soil, youre nute problems come on slow, but are resolved slower, and by the time they do show signs, it can be too late. hydro, any probs will show almost imediatly, and can be cured just as fast, but if you sleep on it too long, bye bye.
ive noticed all my blueberrys are very K sensitive, and heat sensitive. light light feeders(dj short variety which ususally has lots of 3 finger leafs)
do a flush, and then poke some holes with a chopstick, a 1/2" or so out side of the leafs parimeter, the leafs stretch out as far as the roots do. you dont want to be giving this one anymore trouble.
again, looks like a girlie, ill look in my grow bible about those spots, that doesnt look like K probs, but either Mg OD, or N. deficincy. too much Mg and trace elements will give you nute 'lock out'.
i almost want to say, you should poke some holes arounf the lower 1/4 of the pot, to help aeriate the roots some.
it doesnt look like you have churned up the soil at all, id atleast do that, dig in an inch or so and churn it up, get the top soil nice and fluffy.
man, you need same Cannazyme, or Eart Juice Catalyst...! im lucky and the little city i live near has a nice hyroponics shop, very lucky.
if you decide this is how you want to do it, order some Canna nutrients or Eart Jui ce, the stuffs expensive, but will last you a looong time. my eart juice grow bottle lasted me close to a year, with constant growing going on.
Edit: hmm idk man?!? looking through the grow bible what seems the most likely cause is acidic soil
ie. sphagnum peatmoss, there is an excess of iron, and zinc, treat with a flush with a light complete nutrient solution. keep the ph at 5.5 -6.2, low hydroponic levels, those levels will not allow as much of the problamatic micro nutes to get in, and allow for more absorbtion of phosphorus.
arent there any nuseries around? if so, go to one of them and look for some superthrive, and high P bat guano(jamaican). some worm castings are good, or great rather at adding microorganisms to hang around your roots and add some hype + protection general soil stabilization. but, not much, 1/20th of your pots volume.