I'm on day 19 of my grow and am having probs Help Please (pics)

I started my grow 19 days ago i germinated in paper towels in a plastic bag the seeds are from paradise and they are magic bud 50%sativa 50%indica . I got my soil from a grow shop it is cell max future growing it cantains:
Garden Peat
White peat fraction 2-3
Baltic peat
Perlite
Worm Fertiliser
Potting soil mix
Fungus strains and bacteria
Biological fertilizers
PH 5.8/6.5
EC approx. 1.5
The plants spent there first week in small pots under 2x36w compact fluros.
Now they are under a 600w hps 23" minnimum distance from top of plant too the light.
the pots are 4 to 5 litre pots.
The temperature varys from 77 to 92 degrees farenheit i know its hot but i cant seem to change it with the extractor, the humidity goes from 65% to 35% and if i extract or instract it allways puts the humidity down which will hopefully be of use if i make it to flowering.
I watered the girls day 14 aprox then day 19 approx 7 Liters of water between all 10 and i keep the ph of the water at an optimum level with a ph- solution.
The problem started and the edge of one plants leaves turned yellow i thought maybe it was burnted but iv turned the fan up and moved the light away and its still spreading even on the lower leafs. I'm now thinking nutrient deficiency but the soil is supposed to have everything for up until the flowering i'v heard. Heres some pics too Any ideas will be much apreciated as im getting very woried about my girls now.
THANKS FOR READING :-)

Heres some pics of the girls together

You know I really dont see a problem at all....

THose brown spots on leaves can be caused by the leaves dipping on to the dirt, or water or soil getting splashed on them. Those leaves will be long gone anyhow once it starts.

I would say:

1. Try to lower your air temp. I am not sure about all the extractor / intractor whatever that means. Remove the hot air thru a vent and blower fan.

2. Don't worry about the humidity at this point....

3. Water with a pH of 7.0 - 7.5..... that soil seems a little bit acidic.... 5.8 is just too low. Buffer it up with the adjsuted pH range.

4. You dont have nute deficiency. Very hard to have so early.

5. Water a tad bit more often. And water the ENTIRE soil base.

Remember, you are entering the critical phase here, weeks 3 and 4 when the sex will most likely be determined. Don;t stress them from heat and not enuff water. Too much is better than none in my opinion at this time.

Looks good, I would relax and let them grow.

HARD ON

Thanks alot m8 youve put my mind at rest a bit. ill grt my extractor back on to get more hot air out this is my extractor setup it goes to outstde and i can use it to get air in from outside or to take hot air out.

Temperature is to high, bring fresh air in and circulate it often. Your Ph is off too, soil Ph should be 6.3 to 6.8 for best results. With Ph below 6.5 your plant can't uptake needed nutrients like (P) and (Mg) and limited uptake of (Ca). Your plant is not getting enough nutrients of some and to much of others.

You're not using Miracle grow soil are you?

Use the extractor to take hot air out.

Bringing outside air in with a forced fan is ok, but if it is one or the other, choose forcing the hot air out.

Make sure the intake of your exhaust fan is at or near the top of the cabinet as the heat rises.

HAPPY HOT AIR BLOWING :)

Thanks guys the ph of the water is about 6.7 it is the soil that is a bit lower as that is the ph it says on the bag its bought from a grow shop and especially for growing marijuana so i hoped it was ok. Thanks zandor and harddon iv been extracting the air from under the light and it seems a bit better heres the worst affected plant and my extractor setup what do you think ?

Plant looks real good.

You will want to tie that girl down so the bud shoots will delevop. Start slowly and take down about half an inch a day for a week.

As for your air vent system, very creative.

Is that an inlet right next to the outlet?

Make sure the inlet isnt simply sucking the hot air right back in.

Looks good....hows the temps now?

your fans wont be workin to full efficiency cos your ductin all bent an wonky put it so your pullin in a straight line an you'll have more economic productivity from them

Thanks m8 it seems to be cold air coming in but it is from outside so not a great deal of co2. I was thinking about bending but they do seem to be quite bushy hear's a pic of my biggest girl at the mo. I made a scrog on one of the bigger pots to but not shure if i'm gona use it or not yet. Maybe ill just tie and bend. heres a pic of my adjustable scrog too iv only made one so far. I think i'm starting too see some sighns of sex too now but cant quite determin yet theres just 2 hairs on each node so far but no sighns of nut sacks yet thank god.