alright bro.. here is my 2 cents worth..
my instinct says that its a nute def.. not from lack of feeding.. the soil is too "new" to be shorting you on nutes... but from a ph problem in the soil itself... this can not be figured out by ph'ing the water or runoff... well lets take a step back.... this might help...
first you have 3 different ph readings you can get from your plant.. 1) nute solution/water 2) the actual soil ph 3) soil run off ph... all three have very little to do with one another.... the first two are really the only important ones.. run off ph is not accurate for anything since it has not only water/nute solution you just fed, but also all the other shit it washes out of the soil.. it isnt a good measure for anything...
so lets talk about the first two... you always want to ph your nute solution and water that you feed your plants.. keeping that ph in range will ensure that at least some of the nutes that are being fed and absorbed if your soil ph is fucked... in order to check your soil ph you need a soil ph test kit or meter.. they are fairly cheap to expensive.. the pricier the meter/kit the more accurate the reading.. it doesnt have to be the best.. just something to give you an idea where your at.. because if you soil ph is screwed you are in for trouble..
example: you have ph'd your nute solution everytime to around 6.5... but your soil ph is 5.5 for instance (starting out).. well over time the salt that builds up in the soil will cause the ph of the soil to drop more and more.. as it drops certain nutes get locked out more and more.. this causes more and more build up.. ect ect... thats the only time they have something to do with one another...
so the first step is to test your soil ph and see whats up with it...
the second thing it could be (which is my second guess) is that maybe your soil is out of nutes and your plants are lacking some micro nutes... you may want to start feeding not only your macros but a calmag supplement
http://www.wormsway.com/detail.aspx?t=prod&sku=CMP405&AC=1 .. it offers the micro nutes, for the most part, your plant will likely lack...
the best thing to do to avoid all deficiencies is to use a good 3 part nute series (fox farms, gen. hydro., advanced nutes, bc boost) are all great lines to use... and making sure to keep your ph's in check are important too..
http://www.wormsway.com/detail.aspx?t=prod&sku=EJND502&AC=1 this is an example of a product you can use to lower ph.. they also have one to raise it.. there are other ways too we can discuss if you check it and it is indeed out of wack...
now... i dont think heat is a problem.. i had my grow room in the 90s to 100s for a week during my last grow with little problems.. it basically just stopped my plants from growing.. and the 80s is my normal.. low 80s to upper 70s.. i have a fresh air intake so i get plenty of co2.. adding that will help negate the effects of the high temps... really high temps dont matter as much if you can keep plenty of fresh air or co2 available...
last thing.. do you know the ppm of the water you use to feed with?? if the ppm is to high, or it contains a lot of calcium or anything like that, you can get the same sort of problems.. also, do you leave the water out to let the chlorine evaportate?? if not you should do that.. and if at all possible try to find out that info or switch to RO water you get at the store.. it might be somewhat pricey but its worth it in the end...