Aeroflo2 in attic - 5 days flowering, Droopy and yellowing

My first attempt with a hydro grow and I want to make sure I understand all my problems before I reboot at end of summer. So, please educate the newbie b4 he kills the really good seeds!

For next time, I'm getting a Arctica 1/4hp chiller and CO2 system and waiting until fall (or until I can be sure I own the temps). I'm using an AeroFlo2 20 in attic closet (3'x12'x7').

What I really want to know is the other problems that I have and what else I should have learned from this.
* Do the pictures indicate any obvious problems beyond heat?
* Cal-Mag problem? Since I have RO water starting @ 0ppm, should I have added Cal-Mag Plus before adding the nutes? If so, what mix?
* Do I need to suck in fresh air from outside the room?
* Should I intake to the Cool Tubes/exhust from inside the room and leave a vent in the wall for extra intake?
* With the Cool Tubes, should I have put the lights closer then 18" to the tops?

I know I have heat problems, but want to be sure of my fixes next cycle. There were 2 days just before the problems mainfested where air temp exceeded 100 and I'm pretty sure water temp had to get into the 90s as well. Event lasted maybe 1 to 5 hours. I have been able to "manage" the temps better, but it's just not going to keep them into a good range until the fall.... Maybe that's the full study and you can close the book - the heat killed them?

The water temp probably went into the 90's during 2 dark periods on consectivute days (I light from 8pm to 8am and dark from 8am to 8pm). At night when the lights are on, I can keep it between 74 and 84 air temp. I drop a frozen gallow jug of water into the 12 gal res every now and then, but haven't been consistent.

I went to flower about 10 days ago. ppm was about 800 and rose to about 1100. I'm refilling w/ RO water but ppm is sticking around 1000 right now. I don't seem to be getting growth or ph/ppm changes expected. I'm using AN nutes and the SensiBloom recipe.

The room has a 4" AC duct connected to central AC, but no return.

I have a portable AC and oss fan in the room. The 2 lights are 600w, 400w HPS and in Cool Tubes with intake/exhust outside the room. The portable AC exhusts outside the room. I don't much new air makes it in each day.

I was good until 5 days of flowering (12/12). Then, everything started to droop. 2 smaller plants completely drooped but stayed fairly lush green - I cut those down after 2 days of no response but marveled that they stayed green. The bigger plants began to lose their lower to mid leaves and also larger leaves. The leaves yellowed starting at the tips and after 2 days, completed yellowed. The upper leaves are still green but droopy all the time.

Roots have started to brown - they don't look as clean.

There may be limited new growth, but things have certainly slowed down.

Here's more detail...
What is your experience level? - First time.

Your Equipment:
.1) Type and wattage of lights.- 600w HPS, 400w HPS

.2) Distance from tops? - 18 inches

.3) Reflector type? Cool Tube (both lights)

.4) Is there a consistent fresh air supply? No. Light exhust intakes from outside room and exhusts outside room

.5) Do you have an exhaust fan and a circulation fan? Yes but it intakes and exhusts outside of the room. I have 18" ossocilating fan inside the room.

.6) What are the bulb wattages, kelvin ratings, and schedule? 400w and 600w, Kelvin?, 12/12.

Your medium:
.7) Specific brand and type of soil, (coco, peat based soilless...) and anything you've added to it. (vermiculite, perlite, worm castings...) 1x1 rockwool cube in 3" coco pot. Hydron in the pot.

.8) Size of container. - 3" net basket

.9) Did you use peat pucks (or similar) to root clones or germinate seedlings? No

Your nutrients and water:
10) Source of water? (tap, bottled or filtered) What's it's ph before adjusting? R/O, 7.0

11) Method of checking water ph. (ph pen, test strips, aquarium test kit...)
BlueLab meter

12) Method of adjusting water ph. (phosphoric acid, white vinegar, hydrated lime, PH Up...) - PH Down (phosphoric acid)

13) Specific brand and N-P-K ratio for each bottle. List dosages (quantity per gallon) and current feeding schedule. - AN SensiBloom A&B @ 5ml per gallon (half strength)

14) How often are you watering between feedings, and how much per watering? - AeroFlo2 setup, pump runs 24x7, last 5 days of veg until current water level was about 1" below pot and pegs are up about 1.5" from chamber bottom.

15) Any additives or tea's? (Superthrive, CalMag, molasses, Mother's Earth...) Fulvic Acid (4ml/g), carbo load (4ml/g), bud blood (1gr/g)

16) Are your ph levels stable, or do they fluctuate? - Thru veg, ph fluctated as expected. During flowering, ph is not chaning as much but slowly rises each day (<0.2)

17) What is your ingoing water's ph? ...your runoff ph? 5.8 to 6.0 constantly.

18) Do you foliar feed? If so, with what, how often, and at what time do you spray? No.

Your growroom:
19) Indoors or outdoors? - Indoors

20) What size of closet, room or hut? 3' wide x 12' long x avg 7' high. Attic room (ceiling is roof w/ insulation)

21) What are the temps and humidity levels while lights are on? ...With lights off? Lights on = 76 to 84 air, 70 to 82 water. Lights out = 76 to 88 air, 76 to 86 water

22) Have you seen signs of insects in the growroom? Never

Your strain:
23) What strain are you growing? Mixed and unknown. 1 was for sure a Northern Lights hybrid.

24) From seeds or clones? seeds

25) Is this an autoflower strain? no