few issues...need some advice

Hi, I'm new to posting but not new to this forum. I have been reading for months and months. Thank you to everyone that has helped so far. Now here is the backround info....
7x5x8 room in basement
Strain- Feminised Autoflower Haze (3 plants)
18 gallon tote DWC with 7.8L/min pump & 2- 5inch airstones
600watt hps aircooled...but need an inline fan yet 28" above plants (bc temps are so high)
With door open the temp is 83 daytime and 71 darktime 18/6
Res temps with frozen water bottles is around 70.
Ph stays between 5.7-6.2
Oscillating fan 24/7 on plants and a window fan exhausting out the doorway (still need better air exchange...that's the next expense)

I'm using Bonticare grow pro and karma 7tsp of each last res change (5 days ago)
(it recommends for week 1 of veg, 2 tsp per gallon but last week was week 2 from seed and they didn't look like they needed any nutes yet. and I was afraid being autoflower to add more than half recommended for week one of veg.) If that makes sense lol

So the issue is...the brown spots on the lower leaves and curling of top leaves

What I came up with...brown spots...possible nitrogen def? I added 2tsp more grow (still nervous ill over do it with the first feeding...new growth seemed fine till yesterday I noticed brown spots on those too.
Leaves curling ...wind burn or heat stress or both?
By looking at the pics and your experience....do you have any idea what may help?

I'd say the leaf curl is heat stress.

Thank you ak I appreciate the response. Starting week 3 since they sprouted ..........I changed res today. 15 gallons of water...ph'ed, 90 ml of gro (half recom dose for week 2 veg), 15 tsp of karma (also half recom dose). Moved the fans around. Think the osc fan was too close. So its lights out for the afternoon...hoping the spike in nutes will fix the spotting on the new growing leaves (nitrogen def)? Hopefully. Any other comments welcome.

hey royal, first of all res temp in dwc is very important. You could stand to lower than another ten degrees. Try putting in a milk jug, I do that with my 7 gallon res and it gets it down to 60 degrees in about 45 min and it's good for the day. Not only will that provide more oxygen to your roots (which has a very real possibility of suffocating) but the lower temps will actually help counter your ambient room temps. That's my easiest solution for your heat problem.

Secondly, do you have a ppm meter? If so, how old are your plants and what is the ppm. I use botanicare cns formula and the amounts they recommend you using will fry your plants. i believe my grow formula says 15 ml per gallon for seedlings and I use about have that until week 3. Works out to about 400-450 ppm. Week 4 I jump to around 600 ppm. Week 5 is the first full recommended seedling dose of 750. I'm sure my strain is different than yours, mine is finicky with nutes.

Thank you for your advice Destillat. I use big vegetable oil jugs filled with water (frozen) they dethaw so quickly. And take forever to freeze. I put in 2 today instead of 1, and the res temps went down to 65. So I think I am going to put each of the plants in their own 5 gallon dwc. I can control temps a lot easier with simple water bottles I think? The kids are asking why there are so many frozen vegetable oil bottles in the freezer. Oy.
I have 3 Tangerine Dream (fem) (just about 2 wks old from seed). I really want to get a stable enviroment for them all. I have 2 wks till I get the inline fans and exhausts. That should solve the majority of these issues.

Also I moved the oscillating fan much further away and the leaves look drastically better. They don't look so dry and curled.
Its been 11 hrs since their new nutes...no new brown spots so far.

Oh and I do not have a ppm meter! Friday I will get one and follow about what your ppm schedule is! Thank you again!

The 2 ladies that were having the leaf issues (2nd pic) seem to be doing much better. They filled out and started showing pistols all over this past week (3rd pic). So tonight I put them all in their own 5g bkts instead of them sharing 18g totes. Less water and nutes.

So the 2 auto haze girls are at 425 ppm, 1/3 rec. dose bloom, karma, citrus & big bud. Still taking it slow with the nutes.
The other one I started at the same time but ist showing sex yet. It didn't have any leaf spots but it seems to be difficult to please (1st pic, front right).

Thanks again for the help!