Help! Leaves curling and weird spots.

I have 6 plants, 3 weeks from seed. Last night I went out and when I arrived today one of the plants had the tip of its top leaves curling. Another one has some clear spots on its leaves. What might be the problem?
I have one 400w HPS about 20inches above the plants. I water them everyday (it's really hot where I live) until I see some run off. I'm giving them 2ml BioGrow in 5L and Hesi SuperVit. Overwatering? Overfertilizing? Too much light? Heat stress? the other 4 plants are nice. Hope this pics help.

Anyone can help me?

heat from the light is causing the taco look, put a fan on them or move the light up a little

Thank you. They have a fan but I guess it is not enough. I'll move the light and probably buy a better fan. It's only a bit weird that three of them are bigger/taller than this one and they look great. But thanks for your help once again!

Ok, leaves stopped curling but now the yellow spots are getting worse... now 3 plants have yellow spots, including the most advanced (pic 466). Two of them only have a few large clear areas but one of them, apart from that has one of the lower leaves all covered with miniscule yellow spots (pics 461 & 463). I already moved the light from 60cm (23in) to about 80cm (31in) and it is a cooler now. Still, don't think it is the heat that's causing that. pH? Overfeeding? I've been giving them BioGrow, a bit less than 2mL per L of water. I used to water them daily with that but now I did it last Thursday, flushed it Friday, didn't water yesterday and gave it BioGrow again today, at the end of the day. I don't have a pH meter but I guess I'll buy it tomorrow...

Any idea of what this might be?

Your pH may be off, get the meter ASAP...this can result in nutrient lock-out and various other problems, you don't want that!!!

SLB

Well, I'm kinda short on budget so I just ordered one on the internet as it was way much cheaper than at local stores. But it will take some time to get here... the soil I bought states: "pH: 5,0 - 6,5". So, if I was to guess if the pH was too low or too high, which one should I assume? And how should I correct it? The temperature was a bit higher than it should so I changed my setup a little and added one more fan (that I wasn't using so far as they were too little to take it). My camera has no battery but I have it charging as there have been some changes, for the worse :S

Ok. Here are some pics that might help... the first two (pics 470 & 471) to develop these "symptoms", apart from the curling one that is doing fine now, seem to be quite the same as yesterday. But the bigger ones (pics 472 & 473), are looking bad... any guess? Should I give them something for today (it's 11pm here, so I don't have many options...)? Or should I wait until tomorrow, forget the pHmeter I ordered on the internet and buy one tomorrow?

Please help me!

Are you using RO water, or tap? That's definitely nutrient def, but the curling suggests ph is causing it.

I've been using both tap water (I let it evaporate it's Cl for 2 or 3 days) and bottled water. Only one of the plants started curling but I figured out it was the light that was too close. As I moved the lamp a bit it stopped. But by that time the yellow spots and some weird discoloration began a bit all over the place. So... you think it might be nute deficiency? I'm giving it 1,5/2mL of BioGrow per L of water. I water them with that once and then only water for one or two days. If the soil is wet, I don't water at all. Should I give them more nutes? I just don't want to spend 20euros on a pHmeter, when I already bought one on the internet that will take one week or so to get here, if it ain't the pH. Anyone using BioGrow with soil? How much should I feed them?

Ok, went down to the local grow shop and it is closed till the end of the month... I'm f@#$&€ up! I didn't find it in any other store so far! Next weekend I'll travel somewhere nearby to visit another one... till then, should I feed her nutes? Everyday? Or the same frequency but at a higher dose? Please, help me save my babies!

What's your soil again? The def could be caused by lockout caused by the ph being off. What exactly is in your soil? Buy one of the cheap liquid ph test kits, GH makes a good one. Check the ph of your runoff, and ph your water after you add your fert. My bet is that your tap water has a high ph, which is causing some lockout. You will probably need to flush thoroughly with a mild(25%) feed, the fert in the water helps dissolve any salts in the soil.

Trabecula make sure your air exchange is good plenty of fresh air. and it looks like over watering try letting them dry a little. if there heavy water from the bottom for a bit. small plants dont need loads of water or lots of nutrient. to much water can cause root disease and there nasty.whats the RH and temp

First of all, thank you both for your help.

Soil: Compo Sana Universal (compact). From what I understand (my first grow) it's fertilized soil with perlite and agrosil, some shit that stimulates root growth.

Temp: it's hot but it's fresher than it used to be. I will explain. It's been a hot summer here (temps around 40C / 105F) but now I managed (with 3 fans) to drop the temp at the grow room to 80/85. Sometimes a bit more, but I just can't get it better right now. I meant it used to be hotter because I had two small fans only and now I added a good one.

pH: today I got some of those Combur test strips (used for urine at hospitals) and had one of them into the soil for a few minutes. Don't know if shit really worked as it changed a little. If it did, it's something like 5,5/6.

I would try it in the run of water but as you said, I think I was overwatering them. Haven't watered them yesterday nor today and their leaves seem to be clearly raising and the soil is still wet. Even at the top, it's only starting to dry up now. Another thing I was totally stupid about: I transplanted them from the small cups where they were to this pots like 2 weeks ago, maybe less... so probably the "new soil" around them probably has enough nutrients for them.

Probably, overwatering them + BioGrow + Soiçl Fertilizer = nute burn??

What do you think?

Once again, thank you.

heat stress dont trip they will be fine

Yeah, I guess they will
Once again, thank you! Tomorrow I'll go out for a couple of days. When I come back I will report it's progress! Cheers!